Columbia subject headings:
Civilization, Medieval--13th century--Congresses.
Frederick II, Holy Roman Emperor, 1194-1250--Congresses.
Holy Roman Empire--History--Frederick II, 1215-1250--Congresses.
Science, Medieval--Congresses.
Harvard subject headings:
Frederick II, Holy Roman Emperor, 1194-1250--Knowledge of science--Congresses.
Princeton subject headings:
Frederick II, Holy Roman Emperor, 1194-1250--Knowledge of science--Congresses.