Demczyszak, I., D. Włudarczak, M. Fortuna, and J. Zemełko. “The Middle-Aged Women Motivations Taking up Fitness Type Physical Activity”. Journal of Education, Health and Sport, vol. 8, no. 11, Nov. 2018, pp. 382-8, https://apcz.umk.pl/JEHS/article/view/6311.