Roczniak, Katarzyna, et al. “Morphological and Motor Skills Condition Among 10-11 Year Old Children Engaged in Cross-Country Skiing Attending Sports Primary School in Suprasl”. Journal of Education, Health and Sport, vol. 10, no. 6, June 2020, pp. 68-81, doi:10.12775/JEHS.2020.10.06.007.