Nugroho, N. A., S. K. Purnama, S. Riyadi, R. Syaifullah, and D. D. P. Utama. “Serve Exercises With Eastern and Continental Grips Which Is Better for Beginners Improve Skills”. Journal of Human Sport and Exercise, vol. 19, no. 1, Oct. 2023, pp. 15-22, doi:10.14198/jhse.2024.191.02.