Bulgarian-Byzantine Relations During the Reign of Symeon I the Great (893–927). In The Bulgarian State in 927-969. The Epoch of Tsar Peter I: No. XXXIV; Leszka, M. J., Ed.; , Series Ed.; Byzantina Lodziensia; Lodz University Press: Poland, 2018; pp. 35-46. https://doi.org/10.18778/8142-115-7.04.