A Systematic Review of International Entrepreneurship Special Issue Articles

: This paper investigates the body of international entrepreneurship knowledge to identify key trends, research directions and emerging research topics. First, 21 systematic and 6 non-systematic review articles published between 1998 and 2018 are reviewed. The analysis of these 27 review articles explores the trends and directions of development in the ﬁeld, and provides a set of dimensions for evaluating the body of literature. A systematic review of 126 special issue articles using these dimensions proceeds with an assessment of the breadth and depth of international entrepreneurship special issue literature, and provides validation for the key areas and directions of development for international entrepreneurship research. Trends identiﬁed include the convergence between international business and entrepreneurship literatures, the focus on SME internationalization and various forms of international new ventures and born globals. Later years show the emergence of comparative international entrepreneurship and comparative entrepreneurial internationalization as research topics, emphasizing the importance of integrating empirical evidence between countries and contexts. There is a gap in the body of knowledge regarding emerging and transitional country contexts. There is also more room for comparative research that could also support the adaptation and development of context speciﬁc theories, providing a future direction for international entrepreneurship researchers.


Introduction
International entrepreneurship is a substantial contributor to economic sustainability, which is one of the three dimensions of sustainability [1]. The close relationships between economic, social and environmental sustainability, and economic development, are emphasized by economic development theorists [2][3][4][5]. International entrepreneurship is primarily facilitated by small and medium sized enterprises (SMEs), which are key employers and contributors to the economic outputs of modern economies [6]. They also drive the development and use of human capital and R&D [7]. These SMEs are especially important in small and open economies, in order to maintain sustainable development [8,9]. To reap benefits of market integration and economic globalization, foreign market entry of SMEs has become an important government policy issue as well [10]. We aim to review the body of international entrepreneurship knowledge, to contribute to the capacity of scholars and practitioners, to foster sustainable economic development, through better understanding and influencing SME internationalization and other key aspects of international entrepreneurship. Furthermore, it is our aim to better understand the process of the development of the body of knowledge through review articles and special issues, and to articulate implications in terms of further research to be pursued.
International entrepreneurship as a discipline lies at the intersection of international business and entrepreneurship. The term international entrepreneurship was coined by McDougall (1989) [11]. Numerous review articles have been able to systematically capture the extensive portfolio of empirical publications in the constantly evolving field of international entrepreneurship. This article seeks to make a contribution to the body of knowledge of international entrepreneurship in three ways by: (1) providing a review of systematic and non-systematic literature review articles to identify key trends in the direction of research; (2) formulating and validating a set of dimensions in which literature in international entrepreneurship can be assessed to identify gaps in the body of knowledge and (3) identifying key areas open to further research using special issue publications in international entrepreneurship.
Systematic reviews of literature are conducted by the authors as means of capturing the development of knowledge in a particular domain of research. The purpose of making systematic reviews is to address a research problem by identification, critical evaluation and integration of the findings of all relevant (and high quality) studies [12]. Systematic reviews (1) identify and summarize all research on a particular research problem; (2) evaluate and discuss patterns of coverage and gaps in the body of literature; (3) provide an aggregate conceptualization of the theories involved; (4) evaluate, extend and develop these theories; (5) submit implications for policy and practice; and (6) identify directions for further research [13]. Most importantly, systematic reviews represent a higher level of hierarchy of research evidence [14]. Moher et al. (2009) [15] provide a general structure (PRISMA) to guide the development of systematic reviews. Tranfield et al. (2003) [16] give a detailed explanation as to the purpose and role of systematic reviewing in the management discipline that is the overarching domain, encompassing most international business and entrepreneurship research. According to these frameworks [15,16], a systematic screening using specific eligibility criteria is necessary to ensure that studies included in the review are true observations reflective of the research domain reviewed. Furthermore, both emphasize that a particular structure of information is to be extracted and analyzed from the articles, when conducting systematic reviews.
As literature develops and empirical research gets published over time, systematic reviews continue to get outdated and will be in need of updating. However, updating existing structures of systematic reviews, building on the above described, structured extraction and analysis approach may result in self-fulfilling prophecies in terms of their results. Repeating a similar selection technique may lead to the exclusion of new, emerging research themes (and keywords). Relevancy of attributes of research may also change over time due to changing research topics, theories, methods and practices as a consequence of which systematic reviews are becoming outdated and not replicable. Therefore, extending old systematic reviews of literature by searching for new articles using the same keywords, same databases and analyzing them by using the same metrics may miss the articles containing the new topics that have actually been published in the time-frame of the updated search.
Considering the issue of extending systematic reviews of literature and keeping them up to date, a prudent strategy may represent a complete repeat of the systematic review effort, as opposed to a marginal extension of search and analysis in the time frame since the last review. In this case, writing such articles would be exceptionally time consuming due to the high number of new papers that should be included in the review and would become harder to synthesize the results due to the diversity of the relevant research. A common strategy-practiced in several areas of business research-is the progressive specialization on the systematic review of articles namely that scholars opt to focus on a narrow niche area rather than repeatedly conduct review on a broad scale. Another possible strategy would be not to pursue the incremental extension of systematic reviews but to provide a larger scale update, provided that relatively long time has passed since the closing date of the last review, to warrant a sufficient contribution to the body of knowledge.
In this context, we argue that there is a more efficient and effective way to capture the emerging body of knowledge in a research domain. We propose a methodology that relies on reviewing review articles to identify and articulate key trends in a research fields and provide validated examples of the most important attributes of research to be noted and analyzed. Furthermore, we seek an update on the body of literature by exploring articles only published in special issues of periodicals to capture the latest trends, breadth and novelty of the development of knowledge in the area.
Special issues play a particularly important role in disseminating knowledge of management and organizational scholarship. Special issues augment the citation numbers of articles in less prominent journals, enabling these studies to be more impactful [17]. These articles get more citations generally than regular issue ones [18]. Special issues seek novelty and breadth of published research, and have higher potential to interact with the world of practitioners through their ability to capture novelty [17]. They often encourage researchers to submit articles that otherwise would not be devoted to publication, thereby extending the frontiers of research and the dissemination of the results [18]. Special issues also have a positive impact on the acceleration of knowledge development and reduce the time required to publish papers [18]. Therefore, we seek the validation of trends and analytical dimensions extracted from the surveyed studies by systematically reviewing special issue articles in international entrepreneurship.
The remaining part of this paper is structured as follows The next section provides a review of review articles in international entrepreneurship by a network approach to the knowledge generation process of international entrepreneurship. This section is followed by the systematic review and analysis of special issue articles in international entrepreneurship, providing a validation of the results drawn from the systematic reviews and an overview of the main trends and gaps in international entrepreneurship research. The paper is concluded by a synthesis of findings and an articulation of potential future research directions to be pursued.

The Review of Review Articles
Review articles are considered to occupy a high position in the hierarchy of scientific evidence [16,19], and therefore we consider them as authoritative evidence reflecting, first, the state of the art of knowledge at the time the reviews were conducted and, second, a reflection of review practices that evolved specifically in the international entrepreneurship discipline. Therefore, we identified and evaluated review articles to (1) articulate the key trends of development in international entrepreneurship research and (2) to formulate and validate a set of dimensions in which literature in international entrepreneurship can be assessed to identify gaps in the body of knowledge.

Domain Definition of International Entrepreneurship
With intensifying globalization, the liberalization of emerging and transitional markets and their integration into the world economy, interest in international entrepreneurship has soared over the past decades [20]. McDougall and Oviatt (2000) [21] suggest that international entrepreneurship is at the intersection of two disciplines: entrepreneurship and international business.
International entrepreneurship has become a well-established domain of research over the past three decades. One of the earliest explicit definitions of international entrepreneurship originates in McDougall (1989) [11], stating that "international entrepreneurship is defined [ . . . ] as the development of international new ventures or start-ups that, from their inception, engage in international business" (p. 387). Others [22] attribute the first academic coining of the term to Morrow (1988) [23], who highlights that technological progress has led to the opening of new markets internationally, giving rise to international entrepreneurship as a new phenomenon. Wright and Ricks (1994) [24] also include the internationalization of small businesses as a particular part of the domain of international entrepreneurship. International entrepreneurship is "a combination of innovative, proactive and risk-seeking behavior that crosses national borders and is intended to create value in organizations. The study of international entrepreneurship includes research on such behavior and research comparing domestic entrepreneurial behavior in multiple countries" [21] (p. 903). Oviatt and McDougall (2005) [25] use a distinction based on the speed of internationalization, extending the definition previously reliant on the scope of intersection between Sustainability 2018, 10, 3476 4 of 26 these two disciplines. In brief, international entrepreneurship is "the study of new small and young firms that venture abroad" [26] (p. 601). Finally, Jones et al. (2011) define international entrepreneurship as "entrepreneurial behavior [that] involves cross-border business activity, or is compared across countries" [27] (p. 632).
Conceptually, international entrepreneurship rests upon the foundations of entrepreneurship and international business [21]. Therefore, theoretically, international entrepreneurship research encompasses theories of international business (such as the eclectic paradigm, liability of foreignness, transaction cost theory, psychic distance, network theory, international marketing) and entrepreneurship (such as entrepreneurial orientation, decision making, opportunity recognition, risk taking, networking). International entrepreneurship examines phenomena of entrepreneurial internationalization (such as foreign market entry of small and large businesses, early internationalization of international new ventures and born globals), and comparative entrepreneurship (namely cross-country comparison of entrepreneurship, migrant entrepreneurship, and comparative entrepreneurial internationalization) [27]. International entrepreneurship s a diverse discipline and area of research, and has invited several review articles over the past decade, with the objective to validate the merit and identity of the discipline, to identify directions of research and gaps to be pursued, and to aggregate results of prior empirical research (meta-analysis). Therefore, the portfolio of review articles-as described below-was established based on the broadest possible interpretation of international entrepreneurship research, to ensure that it captures all these different areas and approaches.

Selection of Review Articles
Publications in international entrepreneurship have been documented in the Academy of Management Journal since 1994 [28]. Systematic and structured reviews of literature since Cox (1997) [29] have used some or all of the above definitions to scope the body of publications identified. Since then, over 20 review articles have been written demonstrating the prolific nature review writing focusing on the area and also suggesting diversity within the review efforts.
Reviews of literature on international entrepreneurship were sought in global journal databases (such as EBSCOHost, ABI/Inform), using search phrases such as 'international entrepreneurship', 'SME internationalization' and 'systematic review'. These databases have been used in large scale review exercises in business [30]. Key publications were also identified by extracting references from prior systematic review works such as Jones et al. (2011) [27] or Keupp and Gassmann (2009) [26]. This process resulted in the identification of review articles: 21 systematic review papers (journal articles and book chapters), and the snowball review yielded a further 6 non-systematic review papers. Table 1 displays the most frequently used keywords that identify the review articles. These keywords confirm the conceptual antecedents of international entrepreneurship (international business, entrepreneurship, marketing, internationalization, globalization, exports), disclose the key segments of the field (international entrepreneurship, SME internationalization), refer to the directions of theory development (born globals, international new ventures) and identify the means of analysis (bibliometrics/citations). These keywords provide a starting point for the development of a citation network map of review papers.  Figure 1 displays a network of topics and review articles based on an extensive review of the 27 articles identified. The arrows indicate which review articles made reference to which other review articles in defining the scope, methodology or starting point of their reviews, or included them in the set of papers reviewed. The articles are classified as either systematic or non-systematic and based on the conceptual area of the antecedent papers, divided into theoretical thematic groups: international entrepreneurship, SME internationalization or mixed conceptual backgrounds. Those articles that referenced more than one of these conceptual backgrounds were also labelled as partially mixed background articles. Those studies whose antecedents were only articles with mixed backgrounds were termed fully mixed and highlighted in the diagram in a different shade. This differentiation serves the purpose of illustrating the convergence of the conceptual domain in international entrepreneurship and the development of a unified framework based on an initially more fragmented conceptual background. This network of articles may provide evidence for the patterns identified in the domains of management [16], medicine [19] and other sciences [15] in terms of the hierarchy of evidence and aggregation of knowledge by means of systematic reviewing, to be valid for international entrepreneurship. The citation numbers give a quantitative basis for identifying key trends and patterns in terms of how the review articles relate to each other through backward and forward references.  Figure 1 displays a network of topics and review articles based on an extensive review of the 27 articles identified. The arrows indicate which review articles made reference to which other review articles in defining the scope, methodology or starting point of their reviews, or included them in the set of papers reviewed. The articles are classified as either systematic or non-systematic and based on the conceptual area of the antecedent papers, divided into theoretical thematic groups: international entrepreneurship, SME internationalization or mixed conceptual backgrounds. Those articles that referenced more than one of these conceptual backgrounds were also labelled as partially mixed background articles. Those studies whose antecedents were only articles with mixed backgrounds were termed fully mixed and highlighted in the diagram in a different shade. This differentiation serves the purpose of illustrating the convergence of the conceptual domain in international entrepreneurship and the development of a unified framework based on an initially more fragmented conceptual background. This network of articles may provide evidence for the patterns identified in the domains of management [16], medicine [19] and other sciences [15] in terms of the hierarchy of evidence and aggregation of knowledge by means of systematic reviewing, to be valid for international entrepreneurship. The citation numbers give a quantitative basis for identifying key trends and patterns in terms of how the review articles relate to each other through backward and forward references.   Conceptual and synthesis driven literature has progressed over time. Review studies converged between the antecedent fields of research resulting in review articles incorporating mixed theoretical backgrounds. Zahra and George (2002) [22] constructed an integrated model of international entrepreneurship consisting of (1) organizational, (2) environmental and (3) strategic factors, supporting (4) international entrepreneurship, leading to (5) competitive advantages. Rialp et al. (2005) [31] and Coviello and Jones (2004) [32] were the first authors to provide systematic reviews of the domain combining articles from international entrepreneurship and SME internationalization. Peiris et al. (2012) [33] extended the scope of concepts by adding the importance of networks to this model. Kiss et al. (2012) [20] confirmed the applicability of these concepts in emerging markets.

Citation Network Map of Review Articles
Studies focusing on early firm internationalization (including international new ventures and born globals) were also examined in the reviews. Rialp et al. (2005) [31] found that accelerated internationalization shares theoretical approaches with general firm internationalization, but studies also provided evidence that high-tech born globals possess advantages when situated in larger and more advanced markets, which can be explained by environmental factors enabling their access to critical intangible resources, resulting in complex intangible capabilities that create the distinctive strategic features of early internationalizing firms. Keupp and Gassmann (2009) [26] identified antecedents (personal, firm, industry and country level factors), theories (strategy, entrepreneurial orientation, resource-based view, organizational learning, inter-firm organization and competitive advantages) and outcomes (internationalization and firm performance) of early internationalization. Aspelund et al. (2007) [34] confirmed that organizational capacity enhances internationalization performance. Similar performance implications were found by Zou and Stan (1998) [35] and Fillis (2001) [36] and confirmed by means of meta-analysis by Schwens et al. (2018) [37], articulating the importance of knowledge intensity as a catalyst in the relationship between internationalization and firm performance. Dzikowski (2018) [38] [40] pointed out that early internationalization was an important aspect of SME internationalization studies. Fillis (2001) [36] constructed an SME internationalization theory based on reviewing empirical literature focusing on entrepreneurship, marketing and SME research. Built on their review of literature, Covielllo and McAulley (1999) [41] concluded that the SME internationalization process consists of positivistic analysis influenced by the managerial perspective and a relativist evaluation of formal and informal networks resulting in the decision of internationalization and making the choice of the entry mode. Relying on the systematic review of empirical literature, Paul et al. (2017) [42] observed that SMEs require a unique set of strategies, their managers need to present a high entrepreneurial orientation and require unique capabilities to make use of government support. SMEs also benefit in their internationalization efforts by being innovative and exploiting their networks. Wright et al. (2007) [43] emphasized the importance of policy tools in alleviating barriers to SME internationalization.
We develop three hypotheses based on extant literature, in order to evaluate the progression of knowledge in the field of international entrepreneurship, and to validate a framework used to assess special issue articles, with the purpose of identifying trends and gaps in the body of knowledge. Based on the progression of topics and theories indicated in Figure 1 and described above, among the review articles, we hypothesize that review papers progressively build upon each other's results, driving convergence in a field.

Hypothesis 1 (H1).
Later review articles consider previous review articles to progress the body of knowledge. Considering the nature of systematic reviewing, we also anticipate that systematic reviews link more effectively to previous literature, especially previous review literature and are more impactful than non-systematic reviews [16,19]. Therefore, we hypothesize that the number of references made by systematic review articles to previous ones is higher than that of non-systematic review articles.
Hypothesis 2a (H2a). Systematic review articles generate a higher number of references to previous review articles, compared to non-systematic review articles.
Furthermore, we also hypothesize that systematic review articles are referenced more frequently than non-systematic ones due to the higher credibility of systematic reviews.
Hypothesis 2b (H2b). Systematic review articles are referenced more frequently by subsequent ones, compared to non-systematic review articles. Table 2 provides a list of review articles included in this study. The correlation between the number of backward citations of previous reviews and the time passed since publishing is strong, positive and significant (R 2 = 0.747; p < 0.00, n = 27). This provides evidence for the support of Hypothesis 1 and evidence that review studies incrementally build upon one another to expand the body of knowledge.

Bibliometric Analysis of Review Articles
There is a difference between systematic and non-systematic review studies in the number of backward citations. Systematic review studies on average make reference to 3.86 previous review studies, whereas non-systematic review studies reference on average only 1.83 previous reviews. After removing Rialp et al. (2014) [44] as an outlier with reference to 10 previous review studies, the five remaining non-systematic review studies made reference to 0.2 previous review studies on average showing a significant (p < 0.000) difference in the number of backward references between systematic and non-systematic review studies. This supports Hypothesis 2a and implies that while systematic review studies are a continuation of prior review work, non-systematic review studies do not tend to follow the continuous development practice as much.
Finally, there is no significant difference (p = 0.910) in the number of forward citations between systematic and non-systematic review articles. This result does not support Hypothesis 2b and suggests that although systematic review articles tend to build on past review articles more consistently, the impact of systematic and non-systematic reviews does not differ in terms of the number of citations received from other review articles.
Means of searching for articles to be included in the reviews covered most global academic journal databases (ISI Web of science, Scopus, EBSCO, ABI, ProQuest, ScienceDirect, JSTOR), databases operated by publishers (Sage, Taylor and Francis, Springer, Wiley, Emerald) and Google Scholar. A considerable proportion of review articles specifically targeted leading journals in the field only, and many of them also filtered their findings by the ranking of journals in which the relevant articles were identified. Table 3 lists the key search terms used by the review articles to identify suitable papers in the review process for the 21 systematic review articles.  Thirty-six of the 69 different instances of search terms used were the top three topics of international entrepreneurship research. SME internationalization and Small and medium sized enterprises as search terms were only used in 7 instances, constituting only 10% of the search phrases used.

Content Analysis of Review Articles
The 27 review articles were subjected to thematic analysis [54] in order to capture the current state of international entrepreneurship knowledge. Following the process recommended by Saldana (2016) [55] and Yin (2011) [56], themes were identified and noted after reading the review articles themselves. These themes were then consolidated into thematic groups to be evaluated. Thematic analysis was applied to interrogate the review articles, to extract (1) the main purpose of reviewing; (2) the key attributes of articles analyzed in the reviews and (3) [27].
Reviews centered around international entrepreneurship in general or specifically on rapid/early internationalization (INVs, BGs), SME internationalization/exports, comparative international entrepreneurship, methodologies used to research international entrepreneurship, performance and internationalization relationship and emerging market contexts. In the most recent reviews,  Table 4 gives an overview on the purpose of the reviews by identifying their main theoretical focus. 9 of the 27 reviews concentrated on international entrepreneurship as a broad area, 7 on rapid and early internationalization and 6 on SME internationalization. Based on the thematic analysis, a list of the main dimensions in which the review articles evaluated the publications (see Table 5) was derived. The findings converge with the recommendations of Moher et al. (2009) [15] and Tranfield et al. (2003) [16], and highlight that international entrepreneurship scholars use similar metrics in their systematic reviews (including bibliometric methods and citations). It is important to highlight that only one of the 21 systematic reviews performs a meta-analysis of the articles reviewed. Given the diversity of fields, approaches and theories, it seems that meta-analyses may not be feasible. The authors provided extensive arguments supporting the notion that international entrepreneurship is a distinct theoretical area [49,51]. Theoretical antecedents were identified from international business: environment, institutional and network theories, multinational enterprises and subsidiaries, exporting, Uppsala, OLI and TCE frameworks, transaction cost theory, psychic distance and emerging market studies [45,48,50] and entrepreneurship: opportunity evaluation, entrepreneurial orientation and entrepreneur social capital, human capital and other characteristics, firm attributes [40,50] [53] to provide a map in the coverage of literature within the areas already identified as part of international entrepreneurship. Figure 2 provides an overview of the classification of the 27 review articles according to these dimensions, based on the results of the thematic analysis conducted.  Figure 2 shows 66 entries corresponding to the 27 review articles evaluated. It was possible for a review article to fall into multiple categories for both dimensions of classification depending upon the scope and purpose of the review articles. The analysis shows that there is room for further systematic review studies to be conducted targeting SME internationalization and the resource-based view particularly in the domains of comparative international entrepreneurship and comparative entrepreneurial internationalization.
The need for further research specifically identified by reviewers includes more qualitative, exploratory studies [32,36], application of more unified and coordinated methodological efforts moving beyond cross-sectional studies [32] that include multi-level studies [52]. Other authors called for integrating further theoretical perspectives (strategic management, technology innovation, dynamic processes) and additional explanatory variables (measuring networks, capabilities and international entrepreneurial orientation) into explaining SME internationalization, in emerging economies as a context [44][45][46][47]50].  Figure 2 shows 66 entries corresponding to the 27 review articles evaluated. It was possible for a review article to fall into multiple categories for both dimensions of classification depending upon the scope and purpose of the review articles. The analysis shows that there is room for further systematic review studies to be conducted targeting SME internationalization and the resource-based view particularly in the domains of comparative international entrepreneurship and comparative entrepreneurial internationalization.
The need for further research specifically identified by reviewers includes more qualitative, exploratory studies [32,36], application of more unified and coordinated methodological efforts moving beyond cross-sectional studies [32] that include multi-level studies [52]. Other authors called for integrating further theoretical perspectives (strategic management, technology innovation, dynamic processes) and additional explanatory variables (measuring networks, capabilities and international entrepreneurial orientation) into explaining SME internationalization, in emerging economies as a context [44][45][46][47]50].

A Systematic Review of Special Issue Articles
The review of review articles identified three key trends in the direction of development of the field of international entrepreneurship: (1) the convergence of disciplines (international business and entrepreneurship); (2) the establishment of a discipline identity (international entrepreneurship) and (3) focus on specialized areas of international entrepreneurial activity (early internationalization, SMEs). Gaps in the body of knowledge were identified in the area of SMEs and taking the perspective of the resource-based view, in particular for comparative entrepreneurial studies.
The purpose of the systematic review of special issue articles is twofold. Departing from the results of the analysis of the review articles, we use the review of the special issue articles to validate the dimensions of classifying the body of international entrepreneurship knowledge, and progress to the confirmation and further identification of gaps opening up avenues for future research.

Selection of Special Issues and Articles
Moher et al. (2009) [15] provide a general structure (PRISMA) to guide the development of systematic reviews. We use this framework to present the systematic process by which special issue articles were identified and extracted. The process was conducted in two iterations. First, we used a systematic search method to identify the list of special issues in peer reviewed academic that published special issues in international entrepreneurship. Figure 3a shows the details of the selection process of journal special issues. Databases (EBSCOHost and ABI/Inform) were searched for the phrases 'special issue' AND 'international entrepreneurship' with the objective to identify journals special issues in international entrepreneurship. The search was restricted to peer reviewed academic journal articles in English. EBSCO yielded 50 journals with articles identified. The ABI/Inform search resulted in a much higher number (over 800) of journals identified. The next step was to look up every journal identified, to see if they had special issues focusing on international entrepreneurship. To narrow down the large number of journals to be examined, we chose to eliminate those journals from the ABI/Inform search, which had less than 19 articles published in the topic of international entrepreneurship during the examined time period of 1947-2018. The cut-off value of 19 articles identified for a particular journal was selected because the Academy of Management Journal had listed 19 articles for these search phrases, and the Academy of Management Journal is considered an outlet with strong authority in the field [21,28]. Journals identified with less articles listed were considered potentially yielding no result.  Figure 3b shows the second stage of the selection process, in which the special issue articles were evaluated. 137 articles from the 20 special issues were included in the selection process. An additional 15 papers from a dedicated volume published by Routledge were also inserted in the review, providing evidence for the relevancy of this volume to the domain of international entrepreneurship. This volume was identified according to two of the review articles evaluated earlier [44,50]. Of the 152 papers in these 20 special issues and one review volume, 17 items were excluded because they were editorial notes rather than actual academic papers, and another 9 were omitted because despite the fact that they were published in the special issues, they were not actually about international entrepreneurship. The following sections are dedicated to the analysis of these 126 articles. Table 6 contains a list of journals, special issue titles, number of articles extracted using this search process. (The full list of these articles including their full references, topics and conclusions they arrived at, is available from the authors upon request.).  In addition,13 journals were entered into the search portfolio based on the systematic review work of Keupp and Gassmann (2009) [26] and Jones et al. (2011) [27] and the review articles discussed above. Of these 13 journals, 5 new journals were unique and new to the systematic search. After eliminating the duplicates, the 257 unique journals were screened according to journal name and topic focus to eliminate off topic journals. 82 journals were excluded from the evaluation based on this screening. We searched the remaining 157 journals for special issues and looked at the topics of the special issues. Of these journals, 17 published special issues were relevant to the domain of international entrepreneurship and resulted in 20 specific special issues identified. (Three of the journals had two special issues published each). Figure 3b shows the second stage of the selection process, in which the special issue articles were evaluated. 137 articles from the 20 special issues were included in the selection process. An additional 15 papers from a dedicated volume published by Routledge were also inserted in the review, providing evidence for the relevancy of this volume to the domain of international entrepreneurship. This volume was identified according to two of the review articles evaluated earlier [44,50]. Of the 152 papers in these 20 special issues and one review volume, 17 items were excluded because they were editorial notes rather than actual academic papers, and another 9 were omitted because despite the fact that Sustainability 2018, 10, 3476 13 of 26 they were published in the special issues, they were not actually about international entrepreneurship. The following sections are dedicated to the analysis of these 126 articles. Table 6 contains a list of journals, special issue titles, number of articles extracted using this search process. (The full list of these articles including their full references, topics and conclusions they arrived at, is available from the authors upon request.).

Efficiency of the Special Issue Based Review Strategy
In relation to the analysis of the domain of international entrepreneurship, we set out to validate a set of dimensions in which literature in the international entrepreneurship can be assessed (see Figure 2). A systematic review of the full body of international entrepreneurship literature could achieve this, but based on the most recent systematic reviews [37][38][39]42,51,53] this would need to cover over 2000 different articles, resulting in a very laborious review process with diverse outcomes. To improve the efficiency of the review work, we explored the possibility of reliance on articles published in journal special issues, which are higher impact [17] and also relate to the world of practice better [18]. With the consideration of prior results of reviews focusing on special issues in other disciplines [17,18], we expect that special issue papers will have a sufficient coverage of the topics of international entrepreneurship research derived from the systematic reviews, and will identify similar gaps in the body of knowledge. Therefore, we hypothesize that the distribution of review articles and the distribution of special issue articles will not be significantly different, as measured  Hypothesis 3a (H3a). The proportion of review articles and special issue articles falling into the domains of international entrepreneurship research [27] is not significantly different.
Hypothesis 3b (H3b). The proportion of review articles and special issue articles falling into the fields of international entrepreneurship research [53] is not significantly different.  [53]. The 126 articles were classified into 149 categories (some articles belonging to more than one category in the classification). The distribution displayed is similar to the result pertaining to that the of review articles across fields and domains of international entrepreneurship. Specific comparison will need to consider the relative distribution of research papers these categories.   Table 7 demonstrates a comparison of the proportions of review and special issue articles falling into the different domains of international entrepreneurship research [27]. An independent sample ttest was employed [57] to test the difference between the proportion of observations in a particular category, between the review and the special issue articles. There was no significant difference identified between the proportions listed in Table 7. This suggests that Hypothesis 3a is supported when using the classification of the domains of international entrepreneurship [27].  Table 8 shows the proportions of review and special issue articles falling into the different fields of international entrepreneurship research [53]. Significant differences were found in the categories of Conceptual and theoretical synthesis (∆ = 31.3%; p = 0.002), Born globals (∆ = 31.6%; p = 0.005) and International new ventures (∆ = 21.9%; p = 0.045).   Table 7 demonstrates a comparison of the proportions of review and special issue articles falling into the different domains of international entrepreneurship research [27]. An independent sample t-test was employed [57] to test the difference between the proportion of observations in a particular category, between the review and the special issue articles. There was no significant difference identified between the proportions listed in Table 7. This suggests that Hypothesis 3a is supported when using the classification of the domains of international entrepreneurship [27].  Table 8 shows the proportions of review and special issue articles falling into the different fields of international entrepreneurship research [53]. Significant differences were found in the categories of Conceptual and theoretical synthesis (∆ = 31.3%; p = 0.002), Born globals (∆ = 31.6%; p = 0.005) and International new ventures (∆ = 21.9%; p = 0.045). Although the number of articles among the review papers received assignment in multiple categories much more frequently (on average an article was assigned to two categories), the results still confirm that the relative distribution of papers in the fields of international entrepreneurship research is significantly different between the review papers and the special issue articles. Therefore, we conclude that Hypothesis 3b is not supported. Therefore, we can only conclude partial support for Hypothesis 3, which is supported for the domains of international entrepreneurship [27] but not for the fields of international entrepreneurship research [53].

Thematic Analysis of Special Issue Articles
Thematic analysis was applied to interrogate the review articles to extract (1) the main purpose of reviewing; (2) the scope of articles included in the reviews and (3) the key outcomes of the reviews. Table 9 shows the topic focus of the special issues, which shows strong similarity to the distribution of topics presented in the review articles in Table 4. Table 9. Theoretical focus of special issues.

Special Issue Focus Frequency
International entrepreneurship 8 Rapid/early internationalization 5 International entrepreneurship new/future perspectives 4 SME internationalization 3 Developing/emerging economies 1 Source: own study. Figure 5 illustrates the frequency of special issues and number of articles (included in the review) published over time. The first special issue identified was published in 1996. After a longer break, a regular (annual/bi-annual) stream of special issues emerged starting in 2000, peaking twice in the past two decades. In 2005, three special issues were published featuring 15 papers and in 2014, three special issues and an edited volume containing 33 papers. The decade between 2005 and 2014 seems to have been the most prolific period in the publication history of the international entrepreneurship domain internationally. Table 10 is a detailed list of the major conceptual areas and backgrounds used in the special issue articles. Only very few articles relied upon a single conceptual basis, therefore the total count of conceptual bases far exceeds that of the number of articles reviewed. Besides international entrepreneurship theories (such as early internationalization, born globals and international entrepreneurial orientation), general business, international business and entrepreneurship theories dominate the conceptual field with crossovers into psychology, sociology, economics and finance. for Hypothesis 3, which is supported for the domains of international entrepreneurship [27] but not for the fields of international entrepreneurship research [53].

Thematic Analysis of Special Issue Articles
Thematic analysis was applied to interrogate the review articles to extract (1) the main purpose of reviewing; (2) the scope of articles included in the reviews and (3) the key outcomes of the reviews. Table 9 shows the topic focus of the special issues, which shows strong similarity to the distribution of topics presented in the review articles in Table 4.    Table 10 is a detailed list of the major conceptual areas and backgrounds used in the special issue articles. Only very few articles relied upon a single conceptual basis, therefore the total count of conceptual bases far exceeds that of the number of articles reviewed. Besides international entrepreneurship theories (such as early internationalization, born globals and international entrepreneurial orientation), general business, international business and entrepreneurship theories dominate the conceptual field with crossovers into psychology, sociology, economics and finance. Half of the papers aimed at creating or testing theory, by means of exploratory and confirmatory research. The other half of the papers were targeting a contribution to the body of knowledge by evaluating or synthesizing existing knowledge or theories. This suggests a substantial degree of conceptual maturity, in that only 55 of the 126 articles aimed to create new theory by means of empirical investigation, whereas the remaining articles rely upon already existing theory to drive research (see Table 11). Detailed information was extracted from 79 studies regarding the empirical evidence (see Table 12). 42 of these used qualitative and 37 quantitative methods. The average sample size for survey-based regression studies is notably different from secondary data-based regression studies. 108 of 126 articles proposed some areas of further research as shown in Table 13. Specific suggestions for further research can be grouped in two areas: identification of further potential subjects of research and further research designs to be pursued. Authors applying a qualitative methodology mostly recommended the application of quantitative methods for testing their propositions or models. Authors applying quantitative methods on the other hand most commonly suggested the expansion of research efforts to further research subjects or conducting longitudinal analysis. It is also interesting that several authors recommended research in specifically high-tech and low-tech industries suggesting that different results are expected, as well as an expectation of variance across different cultural settings. Quantitative research designs were recommended to progress research ideas related to e-commerce, impact of policy configurations, perception of and reaction to external circumstances and influences, entrepreneurial orientation, effectuation, knowledge and learning, knowledge sharing, influence of networks and internationalization pathways of SMEs, early internationalizing ventures or born globals. On the other hand, qualitative research was proposed by authors whose papers explored more complex problems requiring further theory development such as the development of SMEs, INVs, BGs, dynamic capabilities of firms for internationalization and also in terms of decision making processes, especially with the involvement of more stakeholders. Mixed method research was recommended by authors who explored performance measures and complex models for BGs.
Longitudinal research designs for further research was proposed by researchers whose articles investigated early internationalization of firms, the role of top management teams, the effect of international entrepreneurial orientation distinguishing between born globals and other types of internationalizing and non-internationalizing firms. Their proposals related to the evaluation of factors influencing the speed or process of internationalization, the effectiveness of industry networking and alliances, possibilities and geographical scope of foreign market access and the devise of effective policies supporting firm internationalization and overcoming resource constraints.
Further cross-cultural research was recommended in specific areas of entrepreneurial cognition, alliance formation behavior of SMEs, country specific institutional profiling, venture capital related decision making, competitiveness in foreign markets, explaining modes of internationalization, understanding foreign customers and in the exploration of variation across genders. Examining firms in high-tech and low-tech industries respectively was recommended by studies, which explored the role of technology and R&D in internationalization performance. Extension of research studies into more countries was suggested by authors, who used experience, learning and motivation to explain early internationalization and those having explored the influence of factors such as infrastructure, institutions or firm age on firm internationalization.

Conclusions and Future Research Directions
We set out to achieve three objectives: (1) to develop our understanding as to how knowledge develops through a systematic evaluation of literature; (2) to advance the body of knowledge in international entrepreneurship research by systematically reviewing and evaluating the existing body of knowledge; and (3) to contribute to the capacity of scholars and practitioners to foster economic sustainability through better understanding international entrepreneurship.

Understanding Progress of International Entrepreneurship Research
We conducted a review of systematic and non-systematic review articles with the purpose of identifying how reviews progress the body of knowledge in international entrepreneurship. We hypothesized that: H1: Later review articles consider previous review articles to progress the body of knowledge. We also made the assumption that systematic reviews are more structured and impactful in progressing knowledge compared to non-systematic reviews. Therefore, we hypothesized: H2a: Systematic review articles generate a higher number of references to previous review articles compared to non-systematic review articles; H2b: Systematic review articles are referenced more frequently by subsequent ones compared to non-systematic review articles.
We than progressed to formulating and validating a set of dimensions, based on which a gap in literature can be identified and evaluated. This was done by reviewing review papers and articles published in journal special issues and dedicated book volumes. We assumed that special issue articles capture the breadth and depth of knowledge as much as review articles do. Therefore, we hypothesized: H3a: The proportion of review articles and special issue articles falling into the domains of international entrepreneurship research [27] is not significantly different; H3b: The proportion of review articles and special issue articles falling into the fields of international entrepreneurship research [53] is not significantly different. Table 14 summarizes the results of testing these hypotheses. Our assumptions that review articles progressively build the body of knowledge has been validated (H1 supported), and it is also demonstrated that systematic review articles more consistently capture past review articles, in comparison to non-systematic review articles (H2 supported). Finally, we found evidence that in terms of the domains of international entrepreneurship, review and special issue articles do not show a significantly different coverage (H3a supported). On the other hand, we found evidence that systematic review articles are not necessarily more impactful than non-systematic reviews (H2b not supported) and that special issue articles focus their coverage on cover different fields of international entrepreneurship research compared to review articles (H3b not supported).
These results lead us to conclude that the domains of international entrepreneurship classification [27] will result in similar trends and gaps when used to classify review and special issue articles. In contrast, when employing the fields of international entrepreneurship classification [53], the special issue articles provide a different focus compared to the review articles. Therefore, we conclude that using both domains and fields typology for both types of articles can result in a wider depth and breadth of coverage of the body of knowledge.

Trends and Gaps in International Entrepreneurship Research
The key trend of convergence between the domains of international business and entrepreneurship shaping international entrepreneurship research is evidenced by the network of connections between review articles (shown in Figure 1). The establishment of a disciplinary identity is demonstrated by extensive analysis (citation and thematic analysis) of authors conducting systematic reviews [22,26,49,51,53]. The emerging focus on specialized areas of international entrepreneurship is indicated by the later systematic reviews focusing on SME internationalization [42], born globals [38,39] and comparative studies in entrepreneurship [52] and entrepreneurial internationalization [37].
Future research directions are articulated by specific recommendations of authors as to where more research is needed. This is particularly so when considering review articles. More qualitative and exploratory studies are called for [32,36] and multi-level and multi-method research designs are encouraged [32]. Integration of new theoretical perspectives into international entrepreneurship is invited, which include strategic management, technology innovation, dynamic processes, networks, capabilities, international entrepreneurial orientation [44][45][46][47] and emerging and developing market contexts [50]. Even though a systematic review of literature takes catalogue of emerging and developing market orientated international entrepreneurship research [20], there is more room for research in this direction.
A review of special issue articles allowed us to determine desired research directions in terms of the methods employed to build the body of knowledge. More quantitative research was recommended for e-commerce, impact of policy configurations, perception of and reaction to external circumstances and influences, entrepreneurial orientation, effectuation, knowledge and learning, knowledge sharing, influence of networks and internationalization pathways of SMEs, early internationalizing ventures and born globals. Further qualitative research was encouraged about the development of SMEs, international new ventures, born globals, dynamic capabilities of internationalization and internationalization decision making processes. Mixed methods research was suggested for identifying and validating performance measures of internationalization and to create models of more complex internationalization scenarios (such as born globals and international new ventures). Longitudinal research designs were recommended to better capture early internationalization of firms, the role of top management teams, the effect of international entrepreneurial orientation and to evaluate the effects of factors influencing the speed or process of internationalization, the effectiveness of industry networking and alliances and supportive government policies. Finally, cross-cultural research into entrepreneurship was suggested, focusing on entrepreneurial cognition and decision making, the impact of technology levels on internationalization, SME behaviors and internationalization pathways and the internationalization of R&D focused firms.
The gaps identified by the systematic evaluation of the body of research highlighted (see Figures 2  and 4) the need for more studies using the resource-based view (or dynamic capabilities) and generally a stronger focus on comparative international entrepreneurship and comparative entrepreneurial internationalization. The special issue articles further showed a potential gap in born globals research, although the review articles demonstrated a reasonable coverage of this area, suggesting that there may be some room for further research.

Recommendations for Future Research in International Entrepreneurship
We advanced the body of knowledge in three different ways in this article. First, we provided evidence that systematic review articles are a more effective way of advancing the body of knowledge (H1, H2a). This outcome is aligned with our expectations with regards to the hierarchy of research evidence [14], supporting the methodological prescriptions of systematic reviewing [15,16]. Second, we provided evidence that special issues encompass a wider body of knowledge compared to the more conservative review articles (H3b), which is also aligned with literature discussing the role of special issues in terms of developing and disseminating knowledge [17,18]. Third, we provide a specific evaluation of the body of knowledge captured in special issue articles in international entrepreneurship, which allows us to identify areas promising valuable future directions for research.
Based on the trends and gaps identified, we urge researchers to consider four key directions for future research in international entrepreneurship. First, we recommend filling in the gap in terms of why and how firms-especially early internationalizing firms-internationalize. We urge researchers to adopt a longitudinal perspective on firm internationalization, which could allow exploration of the causality between significant events and influences and provide a better insight into decision making patterns and processes of international entrepreneurs.
The second recommendation is based on the gap identified in terms of the domains of research. There is room for more comparative studies either to seek validation of existing theories, or to provide better contextualization of new research results and theory building, similar to international business [58] and entrepreneurship [59] research.
Third, international entrepreneurship research into emerging and developing markets is identified as an interesting future direction [50]. Despite some research already available in the area [20], the adaptation of existing and development of new, context specific theories as noted above can be achieved by more comparative entrepreneurship and comparative international entrepreneurship research. These domains of international entrepreneurship research are currently relatively under-served as illustrated in Figures 2 and 4.
Finally, we recommend for consideration something that does not seem to have been made either in the systematic reviews or identified when analyzing the breadth and depth of research published in special issues and volumes. We believe that new, hybrid forms of internationalization-especially for smaller firms, departing from smaller markets-need to be given consideration, in which internationalization is not conceived as a set of dimensions (such as speed, geography, etc.) and discrete options or values (such as entry mode choices) but more looked at as a multidimensional continuum, where the parameters defining the outcomes do not only consist of external and internal attributes, but also consider path dependency and strategic orientation at the same time. Such integration of the concepts will enable researchers to adopt a continuum perspective, which may alleviate some of the issues the current development patterns of theory imply, in terms of specialization and isolation of factors and phenomena.

Implications for Sustainable Development and Sustainability Research
Research points towards the importance of SMEs constituting the micro level foundation of sustainable economic development [6]. In a globalizing economic environment, international activities of this cohort of firms drive the local realization of the benefits of economic integration [1], and facilitating their success is becoming a defining role for the public body [7].
As pointed out by Rusu and Roman (2017) [60] entrepreneurship plays a major role in economic development. Our review of the body of knowledge of international entrepreneurship provides further evidence, that international entrepreneurship research examines the micro level foundations of economic development, and both comparative and internationalization focused entrepreneurship research have significant findings to inform sustainable development at the macro level of aggregation.
In particular, as highlighted by Muralidharan and Pathak (2018) [61] the topic of social entrepreneurship carries particular relevancy for sustainability research in entrepreneurship. This direction is exemplified by three special issue articles included in our review; however, a systematic review of international social entrepreneurship research is not conducted as yet. Zahra, Newey and Li (2014) [62] identify the concepts global blended value and global sustainable well-being in relation to international social entrepreneurship. Marshall, Lieberman and Pages (2014) [63] recommend three areas for research in the realm of international social entrepreneurship: (1) traits, motivations and goals; (2) networks and social capital; and (3) cultural competence. Chen, Saarenketo and Puumalainen (2016) [64] operationalize international social entrepreneurship research in the Latin American context, and highlight that it can be regarded as an alternative solution to social problems which governments, NGOs, or for-profit ventures fail to tackle in Latin American environments. These results point out the relevancy of international social entrepreneurship in an emerging economic context, and align with our recommendation that further international entrepreneurship research in necessary in emerging and transitional economies, to facilitate context specific theory building. Research results suggest that international entrepreneurship as a field/sub-field is defined at the intersection of entrepreneurship and international business. Based on citation analysis, it is gradually converging towards becoming a distinct discipline. This is demonstrated by the emergence of particular, highly cited research pieces (articles/chapters) in literature clearly associated with the field.

Etemad & Lee (2003)
• What is the scope for international business theories in international entrepreneurship?
Suggest to include international business theories, such as the role of environment, institutional approaches, multinationals and subsidiaries. Future research directions suggested: market entry and servicing strategies and internationalization of value added activities, measurement of the international environment, entrepreneurial role of subsidiaries, refinement of RBV and innovation theories. • What are the similarities and differences between MNEs and SMEs? International entrepreneurship is an important component of SME internationalization. SME internationalization is driven by the human and social capital of the entrepreneur, firm characteristics and environmental characteristics. Ruzzier et al. (2006) • How to configure policy to support SME internationalization? Supportive policy needs to take into account diversity of SMEs and entrepreneurs that are capable of operating in foreign markets. Policy intervention should alleviate barriers to international expansion (e.g., newness, smallness, inexperience).

Wright et al. (2007)
• How do founding processes, organizational issues and environmental factors effect international marketing strategies of international new ventures?
Early internationalization results in enhanced performance, but the relationship is moderated by organizational capability. Aspelund et al. (2007) • Why does early internationalization work? What resources are required?
Antecedents of early internationalization: personal, firm, industry, country. Elements of early internationalization: strategy, EO, resources, organizational learning, competitive advantage, inter-firm organizations. Outcomes: internationalization, firm performance.

Keupp & Gassmann (2009)
• How can the current body of knowledge reflect on the 5 key questions of international entrepreneurship research?
The relationship of firm age and size to internationalization needs further investigation. Issues such as the profile of the board of directors, strategy orientation and industry factors need to be controlled for in future studies. • How to unify the diverse theoretical landscape of international entrepreneurship?
An integrative model of 5 constructs: entrepreneur, firm, networks, environment and competitive advantage is constructed. Further research is recommended including theories of strategic management, networks and marketing to understand the dynamic processes of international entrepreneurship. Also, more research is recommended in emerging contexts.  • What is the current state of SME foreign market entry-mode choice studies? What future scholarly activity is needed/recommended?
SMEs are different from MNEs in terms of having limited resources, increased sensitivity to external influences and a different ownership structure. Currently used theoretical frameworks include TCE, OLI, institutional theory and network theory. Contextual dimensions include home markets, host markets, psychic distance, industry and firm age.

Laufs & Schwens (2014)
• What is the contemporary research-based knowledge of born global firms? What are the future research directions?
More research is needed to examine the explanations for technological and market strategies, as well as environmental and institutional factors that drive early internationalization. Further research into exploring the role of networks and connections enabling early internationalization is also needed. Finally, questions around the role of founding entrepreneurs, learning and public policies supporting early internationalization need further exploration.

Rialp et al. (2014)
• How did the two parental disciplines of international entrepreneurship shape the future direction of research in the domain?
Influential themes from international business: MNE internationalization, exporting, Uppsala model, TCE framework, emerging economies. From entrepreneurship: opportunity, EO, the entrepreneur. From international entrepreneurship: early internationalization, innovation, networking, international EO, mature born globals. Six areas of potential future research focus: unit off analysis, operationalization of international EO, challenge the TCE/Uppsala frameworks for early internationalizing firms, include corporate entrepreneurship (MNEs and subsidiaries) in research focus, entrepreneurial venturing in emerging economies, opportunity recognition and entrepreneurial decision making.

Dimitratos & Li (2014)
• Is international entrepreneurship a viable spinoff from its parent disciplines?
According to Hambrick & Chen's (2008) framework, international entrepreneurship has reached considerable maturity and acceptance as a theoretical field.

Coviello et al. (2015)
• What is the current state of the art of comparative international entrepreneurship? What are the future directions for research?
Current field is partially situated as a major component of international entrepreneurship. Key possibilities for future research are building and testing holistic frameworks (characteristics, antecedents and outcomes) simultaneously. Consider use of theories from management, international business, economics and entrepreneurship. Develop integrative approaches and multi-level studies.

Terjesen et al. (2016)
• Is international entrepreneurship a field? What are the main characteristics of the research produced? What are the main clusters of references used by research in international entrepreneurship?
The field of international entrepreneurship clusters around five distinct fields of knowledge: (1) SME internationalization; (2)  Øyna and Alon (2018) 1 Some research questions were not stated in this format in the papers reviewed and were inferred by the authors based on the purpose statement articulated in the articles. Source: own study.