On the chromatic index of outerplanar graphs

Abstract Vizing [ Diskret. Analiz 3 (1964), 25–30] has shown that if ϱ denotes the maximum valency of a simple graph, then its chromatic index is either ϱ or ϱ + 1. The object of this paper is to show that the chromatic index of an outerplanar graph G is ϱ if and only if G is not an odd circuit.