Leszka, Mirosław. “The Question of the so-Called Uprising of Konstantin and Fruzhin in Bulgarian Scholarship”. Balcanica Posnaniensia. Acta et studia 21 (January 1, 2014): 5–12. Accessed April 19, 2024. https://pressto.amu.edu.pl/index.php/bp/article/view/1414.