Popiołek, J., M. Kusz, A. Alzubedi, and M. Konopelko. “The Comparison of the Physical Activity Level in Young Adults Assessed With Measuring Tools and Subjective Self-Assessment”. Journal of Education, Health and Sport, vol. 8, no. 9, Sept. 2018, pp. 1436-42, https://apcz.umk.pl/JEHS/article/view/6082.