A theorem of Steinitz [2] states that the triangulations of the 2-sphere can be generated from the triangulation S with four vertices by a process called vertex splitting. That is, given anyâ€¦ (More)

Ever since Taitâ€™s abortive attempt to solve the 4-color conjecture [ 71, geometers have been szarching for Hamiltonian circuits in various types of graphs. Special attention has been given to theâ€¦ (More)

Although questions about Eulerian circuits, paths, and covering edges by edge disjoint paths are easily answered for graphs or directed graphs, they are not easily answered if some edges are directedâ€¦ (More)