Hamrla, Milan. “A Contribution to the Geology of the Senonian Region of the Grdelička Klisura (Grdelica Gorge) in Southern Serbia”. Geologija 1, no. 1 (December 31, 1953): 243–261. Accessed May 3, 2024. https://www.geologija-revija.si/index.php/geologija/article/view/137.