Columbia subject headings:
Fortification--France.
Maginot Line (France)
Harvard subject headings:
Maginot Line (France)
Princeton subject headings:
Fortification--France--History--20th century.
France--Defenses--History--20th century.
France--History, Military--20th century.
France--History--German occupation, 1940-1945.
Maginot Line (France)--Guidebooks.
Maginot Line (France)--History.
Military architecture--France--History--20th century.