Marinow, Kirił. “Settlers, Strongholds, Themes. Byzantine Activities to Strengthen the Border With Early Medieval Bulgaria, 7th–10th C”. Balcanica Posnaniensia. Acta et studia 26 (January 24, 2020): 5–30. Accessed April 23, 2024. https://pressto.amu.edu.pl/index.php/bp/article/view/20525.