Discrete MathematicsVolume 123, Issues 1–3, 15 December 1993, Page 1PrefaceAuthor links open overlay panelY.P. LiuShow moreShareCitehttps://doi.org/10.1016/0012-365X(93)90002-BGet rights and contentUnder an Elsevier user licenseopen archivePrevious article in issueNext article in issueRecommended articlesCited by (0)Copyright © 1993 Published by Elsevier B.V.