Wongwan, P., S. Oupra, and S. Liangprayoon. “Development of English Speaking Ability Baedsed on Communicative Language Teaching (CLT): Case Study in a Language Center”. Chophayom Journal, vol. 30, no. 3, Dec. 2019, pp. 73-82, https://so01.tci-thaijo.org/index.php/ejChophayom/article/view/216612.