关于D－圈存在性的闭包定理

On the Closure Theory of D-Cycles

证明在ｖ≥３的连通图Ｇ中，如果ｕ与ｖ为二不相邻接顶点，且ｄ（ｕ）＋ｄ（ｖ）≥ｖ－１，则Ｇ中有Ｄ圈当且仅当Ｇ＋ｕｖ中有从Ｄ－圈．由此得到了Ｄ－圈存在性定理的一些推广．

Proved that in any 2-conneeted graph with v≥3,if u and v are two non-adjacentvertices, and d(u)+d(v)≥v-1,then G has a D-cycle if and only if G+uv has a D-cycle.From this assertition, we got some generalizations of existence theories about D-cycle.