Columbia subject headings:
Fortification--Conservation and restoration--France--Congresses.
Fortification--France--History--Congresses.
Military architecture--Conservation and restoration--France--Congresses.
Military architecture--France--History--Congresses.
Harvard subject headings:
Fortification--Conservation and restoration--France--Congresses.
Fortification--France--History--Congresses.
Military architecture--Conservation and restoration--France--Congresses.
Military architecture--France--History--Congresses.
Princeton subject headings:
Fortification--Conservation and restoration--France--Congresses.
Fortification--France--History--Congresses.
Military architecture--Conservation and restoration--France--Congresses.
Military architecture--France--History--Congresses.