Vertex-critical graph

Shortly after it was published, Lov z s resolution of the Kneser conjecture was complemented by finding a maximal subgraph having the same chromatic number as the original Kneser graph. To formulate this result, we recall that a graph G is called vertex-critical if for any vertex v G V G), we have x G) = x G-v) + l. 

Sr78] A. Schrijver, Vertex-critical subgraphs of Kneser graphs, Nieuw Arch. Wiskd., III. Ser., (1978), pp. 454-461. 

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