Columbia subject headings:
Castles--Italy--Sicily.
Fortification--Italy--Sicily.
Sicily (Italy)--History--15th-18th centuries.
Harvard subject headings:
Ferdinand V, King of Spain, 1452-1516.
Fortification--Italy--Sicily--History.
Sicily (Italy)--History--15th-18th centuries
Sicily (Italy)--History--15th-18th centuries--Sources.
Princeton subject headings:
Ferdinand V, King of Spain, 1452-1516.
Fortification--Italy--Sicily--History.
Sicily (Italy)--History--15th-18th centuries--Sources.
Sicily (Italy)--History--15th-18th centuries.