สังข์ศรี ส. “A Model of Educational Services to Enable Graduate Students of Sukhothai Thammathirat Open University to Achieve Learning Success in the Distance Education System”. STOU Education Journal, vol. 10, no. 2, May 2018, pp. 65-78, https://so05.tci-thaijo.org/index.php/edjour_stou/article/view/124401.