D. Angelova, “Endodynamic determination and rearrangement of valley systems in Bulgaria at the Pliocene-Quaternary boundary ”, Geog. Fis. Dinam. Quat., vol. 6, pp. 19–24, Jan. 2003, Accessed: Oct. 22, 2026. [Online]. Available: https://gfdq.glaciologia.it/index.php/GFDQ/article/view/1250