Sousa, J. C., H. A. Biswas, and R. Brito. “A Multi Objective Approach to Solve Capacitated Vehicle Routing Problems With Time Windows Using Mixed Integer Linear Programming ”. International Journal of Advanced Science and Technology, Vol. 8, Apr. 2011, pp. 01 -08, http://sersc.org/journals/index.php/IJAST/article/view/15.