Columbia subject headings:
Fiorentino (Extinct city)--History--Congresses.
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Harvard subject headings:
Fiorentino (Extinct city)--History--Congresses.
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Princeton subject headings:
Florence (Italy)--History--To 1421.
Frederick III, King of Sicily, 1272-1337.