R. Kannan, S. Vempala, and A. Veta. FOCS '00: Proceedings of the 41st Annual Symposium on Foundations of Computer Science, page 367. Washington, DC, USA, IEEE Computer Society, (2000)
J. Hao, and J. Orlin. Proceedings of the third annual ACM-SIAM symposium on Discrete algorithms, page 165--174. Philadelphia, PA, USA, Society for Industrial and Applied Mathematics, (1992)