Columbia subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190--Congresses.
Italy, Northern--History--Congresses.
Italy--History--476-1268--Congresses.
Twelfth century--Congresses.
Harvard subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190--Congresses.
Italy, Northern--History--Congresses.
Italy--History--476-1268--Congresses.
Princeton subject headings:
Italy, Northern--Church history--12th century--Congresses.
Italy--History--Germanic rule, 962-1268--Congresses.