Aladžova-Hriščeva, Kina, and Jernej Pavšič. “Nummulites and Calcareous Nannofossils from Lower Eocene Beds in the Area of Veliko Târnovo (North Bulgaria)”. Geologija 31, no. 1 (June 30, 1988): 209–217. Accessed August 7, 2025. https://www.geologija-revija.si/index.php/geologija/article/view/609.