Stoyanov S, Filipova M. RESEARCH OF THE VARIATIONS OF THE ATMOSPHERIC OZONE AND CHANGE OF THE ULTRAVIOLET SUN RADIATION OVER NORTHEASTERN BULGARIA. JSAR [Internet]. 2023 Mar. 4 [cited 2024 Nov. 23];2(1):90-3. Available from: https://jsar.ftn.shu.bg/index.php/jsar/article/view/48