Columbia subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Harvard subject headings:
Princeton subject headings:
Crusades--Sixth, 1228-1229--Congresses.
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Holy Roman Empire--History--Frederick II, 1215-1250--Congresses.
Italy--History--Germanic rule, 962-1268--Congresses.