Klomjit, P., C. Anurattananon, A. Chatmuangpak, and A. Amaluk. “Efficiency Improvement by Simulation Technique in the Parcel Service Company”. Science & Technology Asia, Vol. 25, no. 4, Dec. 2020, pp. 20-29, https://ph02.tci-thaijo.org/index.php/SciTechAsia/article/view/199234.