Columbia subject headings:
Church and state--Holy Roman Empire.
Holy Roman Empire--Church history.
Papacy--History--To 1309.
Harvard subject headings:
Church and state--Holy Roman Empire
Holy Roman Empire--Church history.
Holy Roman Empire--History--Frederick I, 1152-1190.
Holy Roman Empire--History--Frederick II, 1215-1250.
Papacy--History--To 1309
Princeton subject headings:
Church and state--Holy Roman Empire.
Holy Roman Empire--Church history.
Papacy--History--To 1309.