Kalinowski, Paweł, and Katarzyna Judreczka. “Training Elements in Football. Differences in the Training System Between Polish Club and German Club”. Quality in Sport 1, no. 3 (September 30, 2015): 20–27. Accessed April 24, 2024. https://apcz.umk.pl/QS/article/view/QS.2015.014.