Pornchalitkittiporn, Sasipimon, and Tepprasit Gulthawatvichai. 2021. “JOB PERFORMANCE ACHIEVEMENT MOTIVATION OF PERSONAL TRAINER AT FITNESS CENTER IN BANGKOK”. Journal of Sports Science and Health 22 (3). Bangkok, Thailand:370-83. https://he02.tci-thaijo.org/index.php/spsc_journal/article/view/255650.