Columbia subject headings:
Harvard subject headings:
Fortification--Italy--Romagna.
Fortification--Italy--Terra del Sole.
Romagna (Italy)--History.
Terra del Sole (Italy)--Fortifications, military installations, etc.
Terra del Sole (Italy)--History.
Princeton subject headings:
Fortification--Italy--Romagna.
Romagna (Italy)--History.
Terra del Sole (Italy).--History.
Terra del Sole, Italy--Fortifications, military installations, etc.