Mrozkowiak, M., K. Bibrowicz, T. Szurmik, and R. Hadlich. “Correlations and Coexistence of Characteristics Describing Body Posture and Feet in Children and Young People of Both Sexes Aged 7 to 13 Years”. Journal of Education, Health and Sport, vol. 7, no. 5, May 2017, pp. 265-14, https://apcz.umk.pl/JEHS/article/view/4461.