Columbia subject headings:
Harvard subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Germany--History--Hohenstaufen, 1138-1254
Otto IV, Holy Roman Emperor, approximately 1175-1218.
Princeton subject headings:
Frederick II, Holy Roman Emperor, 1194-1250.
Germany--History--Hohenstaufen, 1138-1254.
Otto IV, Holy Roman Emperor, approximately 1175-1218.