Jolkičev, N. (2006). The Cretaceous/Paleogene (K/Pg) boundary in the Mezdra and Lyutidol syncline, Vratza District (West-Fore Balkan, Bulgaria). Geološki Anali Balkanskoga Poluostrva, 67(1), 41-49. https://doi.org/10.2298/GABP0667041J