I. Aprilo, P. E. Arfanda, M. A. Mappaompo, H. Asyhari, M. I. Hasanuddin, and M. I. Syafir, “Development of Tennis Spin Serve Technique Observation Instrument: The Quality Tennis Learning in Higher Education”, IJRER, vol. 4, no. 3, pp. 509–516, Jun. 2025.