Columbia subject headings:
Gregory VII, Pope, approximately 1015-1085.
Guido, Bishop of Ferrara. De scismate Hildebrandi.
Investiture.
Harvard subject headings:
Gregory VII, Pope, approximately 1015-1085
Guido, Bishop of Ferrara. De scismate Hildebrandi.
Investiture
Wido, bp. of Ferrara De Scismate Hildebrandi.
Princeton subject headings: