Dygo, Marian. “Bernard of Clairvaux, Heretics, and Pagans. An Attempt at Interpretation of the Bernard’s Letter on the Wendish Crusade of 1147”. Kwartalnik Historyczny, vol. 127, no. 1, Apr. 2020, pp. 5-32, doi:10.12775/KH.2020.127.1.01.