https://biblioscout.net/article/10.33196/pm200601004902
https://doi.org/10.33196/pm200601004902
https://biblioscout.net/?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=pm&rft.atitle=Niklas+Luhmann%0A%09%09%3B+Einf%C3%BChrung+in+die+Systemtheorie&rft.volume=3&rft.issue=1&rft.spage=49&rft.epage=50&rft.issn=1814-3695&rft_id=info:doi/10.33196/pm200601004902