Siagian, F. R. D., S. Soegiyanto, and D. W. Y. Kusuma. “Analysis of Performance, Commitment, and Self-Concept of Physical Education Teachers in Tanjung Pura-Langkat District”. Journal of Physical Education and Sports, Vol. 8, no. 3, May 2019, https://journal.unnes.ac.id/sju/jpes/article/view/30657.