Columbia subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Holy Roman Empire--History--Frederick II, 1215-1250.
Harvard subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Holy Roman Empire--History--Frederick II, 1215-1250.
Princeton subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Holy Roman Empire--History--Frederick II, 1215-1250.