M. A. Bahauddin, F. A. K. Nissa, R. D. Kurniawati, S. Sulistyarto, and M. Muhammad, “Effects of Structured Psychological Skills Training on Mental Readiness, Performance-Related Abilities, and Character Development in Competitive Volleyball Athletes”, Porkes, vol. 9, no. 1, pp. 446–456, Feb. 2026.