Hansen, Pierre; Kuplinsky, Julio; Werra, Dominique - In: Mathematical Methods of Operations Research 45 (1997) 1, pp. 145-160
A mixed graphG <Subscript>π</Subscript> contains both undirected edges and directed arcs. Ak-coloring ofG <Subscript>π</Subscript> is an assignment to its vertices of integers not exceedingk (also called colors) so that the endvertices of an edge have different colors and the tail of any arc has a smaller color than its head. The...</subscript></subscript>