Vartanyan, Egnara G. “Bulgaria and Russia of the Early 20th Century: From the Correspondence of N. S. Derzhavin With Bulgarian Scientists”. Journal of the Belarusian State University. History, no. 2 (May 10, 2024): 33–40. Accessed October 3, 2026. https://journals.bsu.by/index.php/history/article/view/6007.