Lilov, L. β€œOn the Investigations of Kiril Popoff in the Field of Ballistics (in Bulgarian)”. Ann. Sofia Univ. Fac. Math. and Inf. 98 (December 12, 2008): 11–23. Accessed November 22, 2024. https://stipendii.uni-sofia.bg/index.php/fmi/article/view/125.