1. J. Bartholdy and L. Platzman, “An O(n log n) planar traveling salesman heuristic based on spacefilling curves”, Operations Research Letters, 1:121–125, 1982
2. G. Carpaneto, S. Martello, and P. Toth, “Algorithms and codes for the assignment problem”, in B. Simeone, P. Toth, G. Gallo, F. Maffioli, and S. Pallottino, editors, FORTRAN Codes for Network Optimization, volume 13 of Annals of Operations Research. Baltzer, Basel, 1988
3. D. Casco, B. Golden, and E. Wasil, “Vehicle routing with backhauls: Models, algorithms, and case studies”, in B. Golden and A. Assad, editors, Vehicle Routing: Methods and Studiespages 127–147. North Holland, Amsterdam, 1988
4. N. Christofides and S. Eilon, “An algorithm for the vehicle dispatching problem”, Operations Research Quarterly, 20: 309–3181969
5. G. Clarke and.T. Wright, “Scheduling of vehicles from a central depot to a number of delivery points”, Operations Research, 12(4):568–581, 1964