Columbia subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190--Congresses.
Holy Roman Empire--History--Hohenstaufen, 1138-1254--Congresses.
Harvard subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190--Congresses.
Holy Roman Empire--History--Hohenstaufen, 1138-1254--Congresses.
Princeton subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190--Congresses.
Holy Roman Empire--History--Hohenstaufen, 1138-1254--Congresses.