GACA, Andrzej. Baltic Slavs fighting at sea from the ninth to twelfth century. The phenomenon of over a hundred years of Slavic domination over the Baltic Sea. Studia Iuridica Toruniensia. Online. 9 January 2020. Vol. 24, pp. 51-79. [Accessed 3 July 2024]. DOI 10.12775/SIT.2019.003.