Arif, Arif Purnomo, and Sujarwo Sujarwo. “Instrument Validity and Reliability Confidence to Jump Serve in Volleyball”. JUARA : Jurnal Olahraga 7, no. 1 (December 17, 2021): 151-158. Accessed April 20, 2024. http://jurnal.upmk.ac.id/index.php/juara/article/view/1433.