Columbia subject headings:
Coast defenses--Italy--Sicily--History.
Fortification--Italy--Sicily--History.
Sicily (Italy)--History.
Towers--Italy--Sicily--History.
Harvard subject headings:
Fortification--Italy--Sicily--History.
Sicily (Italy)--Coast defenses--History.
Sicily (Italy)--History
Towers--Italy--Sicily--History.
Princeton subject headings:
Coast defenses--Italy--Sicily--History.
Fortification--Italy--Sicily--History.
Sicily (Italy)--History.
Towers--Italy--Sicily--History.