Columbia subject headings:
Civilization, Medieval--13th century--Congresses.
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Harvard subject headings:
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Holy Roman Empire--History--Frederick II, 1215-1250--Congresses.
Naples (Kingdom)--History--1016-1268--Congresses.
Sicily (Italy)--History--1194-1282--Congresses.
Thirteenth century--Congresses.
Princeton subject headings:
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Holy Roman Empire--Civilization--Congresses.
Holy Roman Empire--History--Frederick II, 1215-1250--Congresses.