Fortuna, M., J. Szczurowski, P. Winiarz, K. Walczewski, and I. Demczyszak. “Estimating the Level of Aerobic Capacity at the Players During the Preparatory Period”. Journal of Education, Health and Sport, vol. 8, no. 3, Mar. 2018, pp. 242-5, https://apcz.umk.pl/JEHS/article/view/5350.