“Professor S. I. Sidelnikov – the eminent Historian of Bulgarian Studies (to the 100 anniversary from the date of a birth)”, The Journal of V. N. Karazin Kharkiv National University. Series: History, no. 51, pp. 154–160, Dec. 2017, Accessed: Oct. 24, 2026. Available: https://periodicals.karazin.ua/history/article/view/9890