1. Maximal covering tree problems;Huston;Transportation Sci.,1989
2. The uncapacitated facility location problem;Cornuejols,1990
3. Geometric Algorithms and Combinatorial Optimization;Grötschel,1988
4. Efficient algorithms for optimization and selection on series-parallel graphs;Hassin;SIAM J. Algebraic Discrete Methods,1986
5. The minimum cost partial covering subtree of a tree;Kim,1989