Generalization of matching extensions in graphs

Let G be a graph with vertex set V (G). Let n; k and d be non-negative integers such that n+2k+d6 |V (G)|−2 and |V (G)|−n−d is even. A matching which covers exactly |V (G)|−d vertices of G is called a defect-d matching of G. If when deleting any n vertices of G the remaining subgraph contains a matching of k edges and every k-matching can be extended to a defect-d matching, then G is called a (n; k; d)-graph. In this paper a characterization of (n; k; d)-graphs is given and several properties (such as connectivity, minimum degree, hierarchy, etc.) of (n; k; d)-graphs are investigated. c © 2001 Elsevier Science B.V. All rights reserved.