Columbia subject headings:
Castles--France--Normandy--History.
Fortification--France--Normandy--History.
Normandy (France)--Defenses--History.
Harvard subject headings:
Castles--France--Normandy--History.
Fortification--France--Normandy--History.
Normandy (France)--Defenses--History.
Princeton subject headings:
Castles--France--Normandy--History.
Fortification--France--Normandy--History.
Normandy (France)--Defenses--History.