Columbia subject headings:
Fortification--France--History--20th century.
France--Defenses--History--20th century.
France. Armée--History--20th century.
Maginot Line (France)--History.
Military architecture--France--History--20th century.
Harvard subject headings:
Fortification--France--History--20th century.
France--Defenses--History--20th century.
France. Armée--History--20th century.
Maginot Line (France)--History.
Military architecture--France--History--20th century.
Princeton subject headings:
Fortification--France--History--20th century.
France--Defenses--History--20th century.
France. Armée--History--20th century.
Maginot Line (France)--History.
Military architecture--France--History--20th century.