Discrete MathematicsVolume 93, Issues 2–3, 25 November 1991, Pages 111-113ForewordAuthor links open overlay panelG.S. Bloom, D.F. HsuShow moreShareCitehttps://doi.org/10.1016/0012-365X(91)90246-XGet rights and contentUnder an Elsevier user licenseopen archivePrevious article in issueNext article in issueRecommended articlesCited by (0)Copyright © 1991 Published by Elsevier B.V.