For a finite graph G let Forb(H) denote the class of all finite graphs which do not contain H as a (weak) subgraph. In this paper we characterize the class of those graphs H which have the property… (More)

Promel, H.J. and A. Steger, Excluding induced subgraphs II: extremal graphs, Discrete Applied Mathematics 44 (1993) 2833294. In this paper we study properties of the classes of graphs not containing… (More)

A graph G = (V,E) is called perfect if G and each of its induced subgraphs has the property that the chromatic number % equals the size a> of a maximum clique. Since their introduction by C. Berge in… (More)

The Steiner tree problem asks for a shortest subgraph connecting a given set of terminals in a graph. It is known to be APX-complete, which means that no polynomial time approximation scheme can… (More)

A fundamental problem in Ramsey theory is to determine or estimate the Ramsey number for complete graphs. WriteR(k) for the smallest integer n with the property that, if one colours the edges of the… (More)

We present a general iterative framework for improving the performance ratio of Steiner tree approximation algorithms. By applying this framework to one specific algorithm we obtain a new polynomial… (More)