Kostova, Irena, Denitsa Apostolova, and Maya Stefanova. “Polycyclic Aromatic Hydrocarbons (PAHs) in Bulgarian Coals: Occurrence, Distribution and Carcinogenicity”. Proceedings of the Bulgarian Academy of Sciences 76, no. 8 (August 29, 2023): 1222–1230. Accessed October 1, 2023. https://proceedings.bas.bg/index.php/cr/article/view/367.