Columbia subject headings:
Church and state--Europe.
Frederick II, Holy Roman Emperor, 1194-1250.
Innocent IV, Pope, approximately 1200-1254.
Harvard subject headings:
Church and state--Europe
Frederick II, Holy Roman Emperor, 1194-1250.
Innocent IV, Pope, -1254.
Innocent IV, Pope, approximately 1200-1254.
Princeton subject headings: