1. Ablay, P. (1979) Optimieren mit Evolutionsstrategien. Doktorarbeit, Fachbereich Wirtschafts- und Sozialwissenschaften, Universität Heidelberg, Heidelberg.
2. Liu, F. and Shen, S. (1998) A route-neighbourhood-based metaheuristic for vehicle routing problem with time windows. Working paper, National Chiao University, Hsinchu, Taiwan.
3. Or, I. (1976) Traveling salesman-type combinatorial problems and their relation to the logistics of blood banking. Ph.D. thesis, Department of Industrial Engineering and Management Science, Northwestern University, Evanston, IL.