An extension of Vizingʹs adjacency lemma on edge chromatic critical graphs Original Research Article

Vizingʹs adjacency lemma describes an important property of edge-chromatic critical graphs. In an edge-chromatic critical simple graph G of maximum degree Δ, if xy is an edge then x is adjacent with at least Δ−deg(y)+1 vertices (≠y) of degree Δ. In this paper, we obtain an extension of this result to multigraphs.