Naveen Garg, Dorit S. Hochbaum. An O(log k) approximation algorithm for the k minimum spanning tree problem in the plane. In Proceedings of the Twenty-Sixth Annual ACM Symposium on Theory of Computing, 23-25 May 1994, Montréal, Québec, Canada. pages 432-438, ACM, 1994. [doi]
Abstract is missing.