Błażejczyk, Krzysztof, Takeshi Morita, Tomoko Ueno-Towatari, Anna Błażejczyk, and Joanna Wieczorek. 2014. “Seasonal and Regional Differences in Lighting Conditions and Their Influence on Melatonin Secretion”. Quaestiones Geographicae 33 (3):17-25. https://doi.org/10.2478/quageo-2014-0026.