INDAH ZUNITA et al. The relationship between self-confidence and concentration with the ability to smash volleyball athletes 12-17 years old in pervas club . Jorpres (Jurnal Olahraga Prestasi), [S. l.], v. 21, n. 2, p. 57–66, 2025. Disponível em: https://jurnal.uny.ac.id/index.php/jorpres/article/view/95718. Acesso em: 23 may. 2026.