Columbia subject headings:
Aragon (Spain)--Foreign relations--Italy--Sicily.
Catholic Church--Foreign relations.
Crusades.
Nicholas IV, Pope, 1227-1292.
Sicily (Italy)--Foreign relations--Spain--Aragon.
Harvard subject headings:
Aragon (Spain)--Foreign relations--Italy--Sicily.
Catholic Church--Foreign relations.
Crusades
Nicholas IV, Pope, -1292.
Sicily (Italy)--Foreign relations--Spain--Aragon.
Princeton subject headings: