Ying Xiao Krishnaiyan Thulasiraman Guoliang Xue QoS Routing in Communication Networks: Approximation Algorithms Based on the Primal Simplex Method of Linear Programming. 815-829 2006 55 IEEE Trans. Computers 7 http://doi.ieeecomputersociety.org/10.1109/TC.2006.109 db/journals/tc/tc55.html#XiaoTX06