KOSTOVA, B.; BORISOVA, I.; PETKOVA, V. The trends in quality changes of the Sofia atmospheric air for a 12-year period. Annual of Natural Sciences Department, [S. l.], v. 5, p. 8–17, 2021. DOI: 10.33919/ansd.19.1.1. Disponível em: https://ojs.nbu.bg/index.php/ANSD/article/view/503. Acesso em: 26 apr. 2024.