Julia Chuzhoy, Venkatesan Guruswami, Sanjeev Khanna, Kunal Talwar. Hardness of routing with congestion in directed graphs. 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 165-178, ACM, 2007. [doi]
Abstract is missing.