Ratajczak, Krzysztof. “Apostolic Legates in Poland in the Middle Ages and Their Key Role in the Adoption of Ecclesiastical Law and Church Legislation by the Polish Church – Educational Aspects”. Biuletyn Historii Wychowania, no. 26, Mar. 2010, pp. 7-18, doi:10.14746/bhw.2010.26.1.