H. L. Abbott

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Consider a graph G and assign to every vertex x of G a set L(x) of colors. Such an assignment L of sets to vertices in G is referred to as a color scheme or briefly as a list for G. An L-colouring of G is a mapping c of V (G) into the set of colors such that c(x) ∈ L(x) for all x ∈ V (G) and c(x) = c(y) whenever xy ∈ E(G). If G admits an L-coloring, then G(More)