Let D be a strong digraph on n ≥ 4 vertices. In [3, Discrete Applied Math., 95 (1999) 77-87)], J. Bang-Jensen, Y. Guo and A. Yeo proved the following theorem: if (*) d(x) + d(y) ≥ 2n-1â€¦ (More)

A cycle in a balanced bipartite digraph is called a pre-Hamiltonian if it contains all the vertices of the balanced bipartite digraph except two. In this paper we give a sufficient condition for theâ€¦ (More)

Let D be a strongly connected directed graph of order n ≥ 4 which satisfies the following condition for every triple x, y, z of vertices such that x and y are nonadjacent: If there is no arcâ€¦ (More)