Botoucharov, Nikola, Alexander Zdravkov, Doris Gross, Irena Kostova, and Achim Bechtel. “Hydrocarbon Potential of Middle Jurassic Sediments (Stefanets Mb. Of Etropole Fm.) from the Western Part of Balkan Orogenic System, Bulgaria”. Proceedings of the Bulgarian Academy of Sciences 75, no. 9 (September 30, 2022): 1317–1324. Accessed January 18, 2025. https://proceedings.bas.bg/index.php/cr/article/view/158.