Zunita, Indah, Christina Fajar Sriwahyuniati, Tomoliyus, and Endang Rini Sukamti. “Relationship Between Self-Confidence and Concentration With the Smashing Ability of 12-17 Year Volleyball Athletes at the Pervas Club”. Indonesian Journal of Sport Management 5, no. 4 (November 29, 2025). Accessed June 13, 2026. https://www.ejournal.unma.ac.id/index.php/ijsm/article/view/16184.