KILANOWSKA, Jolanta and MUSZKIETA, Radosław. Physical activity as one of the elements of healthy behavior. Comparative analysis of 11-, 12- and 13-year-old students in selected schools in Poland and Norway. Pedagogy and Psychology of Sport. Online. 16 November 2019. Vol. 5, no. 2, pp. 191-208. [Accessed 27 July 2024]. DOI 10.12775/PPS.2019.05.02.001.