Julia Chuzhoy, Sanjeev Khanna. Polynomial flow-cut gaps and hardness of directed cut problems. In David S. Johnson, Uriel Feige, editors, Proceedings of the 39th Annual ACM Symposium on Theory of Computing, San Diego, California, USA, June 11-13, 2007. pages 179-188, ACM, 2007. [doi]
Abstract is missing.