Physical Activity as a Predictor of the Level of Stress and Quality of Sleep during COVID-19 Lockdown. - Lipert, Anna; Kozłowski, Remigiusz; Timler, Dariusz; Marczak, Michał; Musiał, Kamila; Rasmus, Paweł; Kamecka, Karolina; Jegier, Anna (International Journal of Environmental Research & Public Health, 2021)