The Concept of heresy in the Middle Ages (11th-13th c.) : proceedings of the international conference [held by the Institute of Medieval Studies] Louvain, May 13-16, 1973 / edited by W. Lourdaux and D. Verhelst. - Lourdaux, Willem, 1923-1989. (OLS)http://pul/name/5139; Verhelst, Daniël, C.I.C.M., 1933- (OLS)http://pul/name/5140; Katholieke Universiteit te Lovanio (1970- ). (OLS)http://pul/name/79656 (Leuven University Press, 1976)
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