摘要
At the Fourth International Conference on Graph Theory and Applications (1980), G. Chartrand posed the following problem: If a graph G contains spanning trees with m and n end-vertices, respecfively, where m<n, does G contain a spanning tree with k end-vertices for every integer k where m< k<n? Recently, the problem has been settled by S. Schuster and Cai Maocheng, independently. Here we shall introduce a simpler proof.
