Columbia subject headings:
Holy Roman Empire--History--To 1517.
Sicily (Italy)--History--1194-1282.
Sicily (Italy)--History--1282-1409.
Harvard subject headings:
Henry VI, Holy Roman Emperor, 1165-1197.
Holy Roman Empire--History--To 1517.
Rudolf I, King of Germany, 1218-1291.
Sicily (Italy)--History--1194-1282
Sicily (Italy)--History--1282-1409
Princeton subject headings:
Church and state--Holy Roman Empire.
Church and state--Italy--Sicily.
Holy Roman Empire--History--843-1273.
Sicily (Italy)--History--1194-1282.
Sicily (Italy)--Politics and government--To 1282.