Mrozkowiak, Mirosław, Karol Bibrowicz, Roland Hadlich, Piotr Kurzeja, and Tomasz Szurmik. 2017. “Correlations and Coexistence of Characteristics Describing Body Posture and Feet in Children of Both Sexes Aged 4 to 6 Years”. Journal of Education, Health and Sport 7 (5):225-64. https://apcz.umk.pl/JEHS/article/view/4459.