Meechusup, T. (2009) “Value Creation for Audio Learning Service of Working Age Population in Bangkok”, Journal of Business, Innovation and Sustainability (JBIS), 4(1), น. 103–110. available at: https://so02.tci-thaijo.org/index.php/BECJournal/article/view/54050 (สืบค้น: 11 ธันวาคม 2025).