Vardges Melkonian, Éva Tardos. Approximation Algorithms for a Directed Network Design Problem. In Gérard Cornuéjols, Rainer E. Burkard, Gerhard J. Woeginger, editors, Integer Programming and Combinatorial Optimization, 7th International IPCO Conference, Graz, Austria, June 9-11, 1999, Proceedings. Volume 1610 of Lecture Notes in Computer Science, pages 345-360, Springer, 1999. [doi]
Abstract is missing.