Let be an undirected graph with a weight function and a costfunction on edges. The constrained minimum spanning tree problem is to find aminimum cost spanning tree T in G such that the total weight in T is at most a given bound B. In this paper, we present two polynomial time approximation schemes (PTASs) for the constrained minimum spanning tree problem.
"Polynomial Time Approximation Schemes for the Constrained MinimumSpanning Tree Problem." J. Appl. Math. 2012 (SI03) 1 - 8, 2012. https://doi.org/10.1155/2012/394721