Harold N. Gabow. Special edges, and approximating the smallest directed ::::k::::-edge connected spanning subgraph. In J. Ian Munro, editor, Proceedings of the Fifteenth Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2004, New Orleans, Louisiana, USA, January 11-14, 2004. pages 234-243, SIAM, 2004. [doi]
Abstract is missing.