Machfud, Ali, Febrian Dwicahyo, and Muhammad Wahyono. “Pengetahuan Mahasiswa Fakultas Ilmu Keolahragaan Universitas Negeri Surabaya Tentang Alat Olahraga Gym Ball”. Journal of Sport and Exercise Science 1, no. 1 (March 30, 2018): 01–07. Accessed December 11, 2025. https://journal.unesa.ac.id/index.php/jses/article/view/2419.