Gregory the Great and Gregory VII : A comparison of their concepts of renewal / Gerhart B. Ladner; with a note on the computer method used by David W. Packard. - Ladner, Gerhart B. (Gerhart Burian), 1905-1993. (OLS)http://pul/name/15121; Packard, David W. (OLS)http://pul/name/60865 (Edizioni di Storia e Letteratura, 1983)