Sodsoon, Suphan, Sarayut Kornvirat, and Nakhon Sodsoon. 2014. “Applications of a Saving Method With Max-Min Ant System to a Vehicle Routing Problem With Time Windows and Speed Limits”. Engineering and Applied Science Research 41 (2):243-52. https://ph01.tci-thaijo.org/index.php/easr/article/view/21796.