Trajdos, T.M. 1985. Metropolitans of Kiev Cyprian and Grzegorz Camblak (Bulgarian Orthodox priests) and the problems of Orthodox Church in the Polish-Lithuanian state during last years of 14th and first quarter of t15th centuries. Balcanica Posnaniensia. Acta et studia. 2, (Dec. 1985), 211–234. DOI:https://doi.org/10.14746/bp.1985.2.16.