2GEORGE I, MANOLIS K, GREGORY P. A Problem Generator-solver Heuristic for Vehicle Routing with Soft Time Windows [J]. Omega, 2003, 31: 41-53.
3GREGORY G, ANDERS Y. Polynomial Approx Imation Algorithms for the TSP and the QAP with a Factorial Domina- tion Number[J]. Discrete Applied Mathematics, 2002, 119: 107-116.