LESZKA, Mirosław J. The Byzantines in the service of the Bulgarian rulers in the first half of the 9th century. Przegląd Nauk Historycznych, Łódź, v. 16, n. 3, p. 213–224, 2017. DOI: 10.18778/1644-857X.16.03.09. Disponível em: https://czasopisma.uni.lodz.pl/pnh/article/view/3189. Acesso em: 5 lip. 2024.