Bogdevičiene, Viktorija, Milda Pečiuliene, and Aloyzas Girgždys. “Changes of Natural Ionizing Radiation in Anthropogenic Objects”. Journal of Environmental Engineering and Landscape Management 13, no. 3 (September 30, 2005): 103-107. Accessed October 14, 2019. https://journals.vgtu.lt/index.php/JEELM/article/view/8044.