Khanina, Naila, et al. “The Effect of Ladder Drill Training on Speed and Agility Improvement in Junior Badminton Athletes Aged 11-14 Years”. Journal of Racket Sports Performance & Science (JRSPS), vol. 1, no. 1, Nov. 2025, pp. 8-15, https://journal.unesa.ac.id/index.php/jrsps/article/view/47216.