Jitngamplang, B., and S. Thampitug. “Thailand’s Potentials as World’s Gems and Jewelry Manufacturing Center and Trading Hub”. Ph.D. in Social Sciences Journal, vol. 9, no. 1, Apr. 2019, pp. 30-43, https://so05.tci-thaijo.org/index.php/phdssj/article/view/110400.