摘要

Let a, b and k be nonnegative integers with 2 <= a < b and b equivalent to 0 (mod a 1), and let G be a graph of order n with n >= (a+b-1)(2a+b-4)-a+1/b + k. A graph G is called an (a, b, k)-critical graph if after deleting any k vertices of G the remaining graph of G has an [a, b]-factor. In this paper, it is proved that G is an (a, b, k)-critical graph if vertical bar NG(X)vertical bar > (a - 1)n + vertical bar X vertical bar + bk - 1/a + b - 1 for every non-empty independent subset X of V(G), and delta(G) > (a - 1)n + b + bk/a + b - 1 Furthermore, it is shown that the result in this paper is best possible in some sense.