Okoniewska, Monika. “Diurnal Course of Cloud Cover in Poland in the Following Decades of the Year (based on Years 1990-2000)”. Journal of Education, Health and Sport 6, no. 10 (January 4, 2017): 730–740. Accessed June 28, 2025. https://apcz.umk.pl/JEHS/article/view/4137.