Dolchinkov, Nikolay, and Nikolay Nichev. “GAMMA-BACKGROUND RADIATION CONTROL SYSTEMS AS A FACTOR OF BULGARIA’S NATIONAL SECURITY”. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 4 (June 22, 2024): 83–88. Accessed November 22, 2024. https://journals23.rta.lv/index.php/ETR/article/view/8225.