Columbia subject headings:
Cultural property--Protection--Congresses.
Historic sites--Conservation and restoration--Congresses.
Harvard subject headings:
Architecture--Conservation and restoration--Congresses
Historic sites--Conservation and restoration--Congresses.
Princeton subject headings:
Architecture--Conservation and restoration--Congresses.
Cultural property--Protection--Congresses.
Historic preservation--Congresses.
Historic sites--Conservation and restoration--Congresses.
Ruins--Congresses.