Petrovic, A. S. and Carevic, I. Z. (2015) “Geological influence on the formation of Samar natural bridge and collapse valley of Ravna River from the NE Kučaj Mountains (Carpatho-Balkanides, eastern Serbia)”, Acta Carsologica. Ljubljana, Slovenija, 44(1). doi: 10.3986/ac.v44i1.898.