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^Куйо М. Куев (1967). Черноризец Храбър (in Bulgarian). Изд-во на Българската академия на науките.
^Dimitri Obolensky (2004). The Bogomils: A Study in Balkan Neo-Manichaeism. Cambridge University Press. p. 92. ISBN0-521-60763-9.
^Omoniyi, Tope; Fishman, Joshua, eds. (2006). Explorations in the Sociology of Language and Religion. John Benjamins Publishing. p. 61. ISBN978-902-722-710-2.
^Simon Franklin (2019). The Russian Graphosphere, 1450-1850. Cambridge University Press. p. 46. ISBN978-110-849-257-7.