Penov, Nikolay, Guergana Guerova, and Anastasiya Stoycheva. “Fog Climatology and Stability Index for Plovdiv 1991–2018”. Proceedings of the Bulgarian Academy of Sciences 75, no. 8 (August 31, 2022): 1156–1164. Accessed July 25, 2024. https://proceedings.bas.bg/index.php/cr/article/view/137.