Noor Noveminaila, Nabella, Soegiyanto Soegiyanto, and Setya Rahayu. 2020. “The Effect of Arm Strength, Leg Muscles, Torso Flexibility on The Improvement of Butterfly Stroke Swimming Exercise”. Journal of Physical Education and Sports 9 (2), 166-71. https://journal.unnes.ac.id/sju/jpes/article/view/41077.