Tran, T., and M. A. A. Clariño. “Solving Multi-Pickup and Delivery Problem With Time Windows Using Ant Colony Optimization”. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), vol. 13, no. 4, Dec. 2021, pp. 35-41, https://jtec.utem.edu.my/jtec/article/view/6144.