收缩临界6连通图中的6度顶点

Vertices of Degree 6 in Contraction-Critical 6 Connected Graphs

证明对于收缩临界6连通图中的任一个6度点x,或者它与一个6度点相邻,或者在它的邻域中存在一点y,在y的邻域中一定有2个相邻的6度点.

It is proved that for each vertex x of degree 6 in a contraction-critical connected graph either there is a neighbor of degree 6 of x, or there exists a vertex y in N（x） such that there are two adjacent vertices of degree 6 in the neighborhood of y.