Kocjan, J. “Physical Activity Level and Health-Related Quality of Life (HRQOL) in Amateur Tennis Players. Comprehensive Evaluation of Factors and Components of Subjective Self-Assessment of Health”. Journal of Education, Health and Sport, vol. 5, no. 6, June 2015, pp. 375-83, https://apcz.umk.pl/JEHS/article/view/2756.