Columbia subject headings:
Harvard subject headings:
Europe--History--476-1492--Congresses.
Germany--History--Hohenstaufen, 1138-1254--Congresses.
Hohenstaufen, House of--Congresses.
Holy Roman Empire--History--Congresses.
Holy Roman Empire--History--Hohenstaufen, 1138-1254--Congresses.
Princeton subject headings:
Hohenstaufen, House of--Congresses.
Holy Roman Empire--History--Hohenstaufen, 1138-1254--Congresses.