Kokoszko, M., and M. J. Leszka. “Naval Fire/Liquid Fire. Byzantine „Miracle” Weapon and the Question of Its Familiarity to the Bulgarians Between the 7th and 11th Century”. Fasciculi Archaeologiae Historicae, vol. 25, Jan. 2012, pp. 9-15, https://journals.iaepan.pl/fah/article/view/1448.