Ditamapai, J., N. Sirivongpaisal, and S. Suthummanonsal. “A Study of Physical Distribution Model in Suratthani Province”. Engineering and Applied Science Research, vol. 38, no. 2, May 2012, pp. 129-37, https://ph01.tci-thaijo.org/index.php/easr/article/view/1602.