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"Pope St. Gregory VII," Catholic Encyclopedia; retrieved 2011-12-1.

Society for the Diffusion of Useful Knowledge. (
1838). "
Gregory VII," Penny cyclopaedia, Vol.
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Douglas, J. James Dixon. (
1992). "
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"List of Popes," Catholic Encyclopedia (2009); retrieved 2011-12-1.
"Pope St. Gregory VII," Catholic Encyclopedia; retrieved 2011-12-1.
Society for the Diffusion of Useful Knowledge. (1838). "Gregory VII," Penny cyclopaedia, Vol. 11, pp. 444-446.
Douglas, J. James Dixon. (1992). "Gregory VII," Who's Who in Christianity, p. 288.
Pope Gregory VII