Dharmendra Kumar Gupta Tabu Search for Vehicle Routing Problems (VRPs). 693-701 2002 79 Int. J. Comput. Math. 6 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=0020-7160&volume=79&issue=6&spage=693 db/journals/ijcm/ijcm79.html#Gupta02