Marinow, Kirił. “Wild, Haughty and Menacing Highlanders: Bulgarians and Mountains in the Context of Byzantine-Bulgarian Armed Conflicts”. The Bulgarian State in 927-969. The Epoch of Tsar Peter I: No. XXXIV, edited by Mirosław J. Leszka, Lodz University Press, 2018, pp. 287-01, https://doi.org/10.18778/8142-115-7.16.