Pentek, Z. 2020. Cologne marks or French livres, or financing and currency conversions during the 4th Crusade, in the light of the agreement of April 1201 and the chronicles of Geoffroy de Villehardouin and Robert of Clari. Balcanica Posnaniensia. Acta et studia. 26, (Feb. 2020), 83–92. DOI:https://doi.org/10.14746/bp.2019.26.5.