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