Constance Brittain Bouchard, Sword, Miter and Cloister. Nobility and the Church in Burgundy, 980-1198, Ithaca/Londres, Cornell Univers. Pres., , 463 p. (lire en ligne), p. 410.
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(en) Uta-Renate Blumenthal, The Investiture Controversy: Church and Monarchy from the Ninth to the Twelfth Century, University of Pennsylvania Press, (ISBN978-0-8122-0016-4, lire en ligne)