The(△+2,2)-incidence coloring of outerplanar graphs

An incidence coloring of graph G is a coloring of its incidences in which neighbody incidences are assigned different colors.In this paper,the incidence coloring of outerplanar graphs is discussed using the techniques of exchanging colors and the double inductions from the aspect of configuration property.Results show that there exists a(△ 2,2)-incidence coloring in every outerplanar graph,where △ is the maximum degree of outerplanar graph.