PAVILAS, C., and C. CHAIWATCHARAPORN. “COMPARISION IN MAXIMUM BALL VELOCITY OF 3-STRUCTURAL CHARACTERISTIC RACKETS USING SIMULATED TENNIS FLAT SERVE”. Journal of Sports Science and Technology, vol. 14, no. 2, Dec. 2014, pp. 1-16, https://he01.tci-thaijo.org/index.php/JSST/article/view/44134.