Columbia subject headings:
Emilia-Romagna (Italy)--History, Military.
Fortification--Italy--Emilia-Romagna--History.
Fortification--Italy--Marche--History.
Marche (Italy)--History, Military.
Harvard subject headings:
Castles--Italy--Emilia-Romagna.
Castles--Italy--Marche.
Emilia-Romagna (Italy)--History, Military.
Fortification--Italy--Emilia-Romagna--History.
Fortification--Italy--Emilia-Romagna.
Fortification--Italy--Marche--History.
Fortification--Italy--Marche.
Marche (Italy)--History, Military.
Princeton subject headings:
Emilia-Romagna (Italy)--History, Military.
Fortification--Italy--Emilia-Romagna--History.
Fortification--Italy--Marche--History.
Marche (Italy)--History, Military.