H-colorings generalize traditional graph colorings, and are of interest in the study of grammar interpretations. Several authors have studied the complexity of the H-coloring problem for variousâ€¦ (More)

It is standard practice among authors discussing the minimum spanning tree problem to refer to the work of Kruskal(1956) and Prim (1957) as the sources of the problem and its first efficientâ€¦ (More)

Let H be a fixed graph. We introduce the following list homomorphism problem: Given an input graph G and for each vertex v of G a ``list'' L(v) V(H), decide whether or not there is a homomorphism f :â€¦ (More)

List homomorphisms generalize list colourings in the following way: Given graphs G; H , and lists L(v) V (H); v 2 V (G), a list homomorphism of G to H with respect to the lists L is a mapping f : Vâ€¦ (More)

A. Vince introduced a natural generalization of graph coloring and proved some basic facts, revealing it to be a concept of interest. His work relies on continuous methods. In this note we make someâ€¦ (More)

A perfect matching in a graph H may be viewed as a collection of subgraphs of H, each of which is isomorphic to K2, whose vertex sets partition the vertex set of H. This is naturally generalized byâ€¦ (More)

We survey the theoretical results obtained for wavelength routing in allâ€“optical networks, present some new results and propose several open problems. In allâ€“optical networks the vast bandwidthâ€¦ (More)