On the SOMA-cube-puzzle H.-D. GRONAU; H.-H. LARISCH — 1981 Beiträge zur Algebra und Geometrie = Contributions to algebra and geometry
Path systems in acyclic directed graphs H. D. O. F. Gronau; W. Just; W. Schade; Petra Scheffler; J. Wojciechowski — 1987 Applicationes Mathematicae