Piotr Berman, Marek Karpinski. 8/7-approximation algorithm for (1, 2)-TSP. In Proceedings of the Seventeenth Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2006, Miami, Florida, USA, January 22-26, 2006. pages 641-648, ACM Press, 2006. [doi]
Abstract is missing.