Lateh, A., S. Suthammanon, N. Sirivongpisal, and M. Tehyo. “Solving a Vehicle Routing Problem With Time Window for Transportation Service Planning for Elderly People: A Case Study of Hatyai District Songkhla Province”. Princess of Naradhiwas University Journal, vol. 11, no. 2, Apr. 2019, pp. 117-31, https://li01.tci-thaijo.org/index.php/pnujr/article/view/132835.