Aftanasiuk, Maryla. “Physical Fitness of Urban and Rural Schoolchildren from Low Social Strata in Yucatan, Mexico”. Studia Ecologiae et Bioethicae 1, no. 1 (December 31, 2003): 127–140. Accessed July 16, 2024. https://czasopisma.uksw.edu.pl/index.php/seb/article/view/6796.