It is shown that for a set S of n pairwise disjoint axis-parallel line segments in the plane there is a simple alternating path of length ( n). This bound is best possible in the...
We give a bound on the reconstructibility of an action G X in terms of the reconstructibility of a the action N X, where N is a normal subgroup of G, and the reconstructibility o...
A map is a connected topological graph cellularly embedded in a surface. For a given graph , its genus distribution of rooted maps and embeddings on orientable and non-orientable s...
An n-partite tournament is an orientation of a complete n-partite graph. An npartite tournament is a tournament, if it contains exactly one vertex in each partite set. Douglas, Pr...