二部图K(m,n)-A中的色正规图类

设Ｐ（Ｇ，λ）表示简单图Ｇ的色多项式。简单图Ｈ称为与Ｇ是色等价的（记作Ｈ￣Ｇ），如果Ｐ（Ｈ，λ）＝Ｐ（Ｇ，λ）。简单图类Ｌ称为色正规图类，若对任意Ｈ，Ｇ∈Ｌ使Ｈ￣Ｇ都有Ｈ与Ｇ同构。

Classes of Chromatically Normal Graphs of Bipartite Graphs K(m,n)-A

Let G be a simple graph and P(G,λ) denote the chromatic polynomial of G. Then two simple graphs H and G are said to be chromatically equivalent (in notation: H～G) if P(H,λ)=P(G,λ). A class of graphs L is said to be a class of chromatically normal graphs if for any graphs H,G∈L,H～G implies that H is isomorphic to G.Let K(m,n)-A denote the bipartite graph obtained by deleting a set of edges A from a complete bipartite graph K(m,n).Let L-s2={K(m,n)-A||A|=s,n≥m>s}.In this paper we prove that L-22,L-32 and L-42 are classes of chromatically normal graphs.