Columbia subject headings:
Building stones--Deterioration--Congresses.
Monuments--Conservation and restoration--Congresses.
Harvard subject headings:
Building stones--Conservation and restoration--Congresses.
Building stones--Deterioration--Congresses.
Monuments--Conservation and restoration--Congresses.
Sculpture--Conservation and restoration--Congresses.
Princeton subject headings:
Building stones--Conservation--Congresses.
Building stones--Deterioration--Congresses.
Monuments--Conservation and restoration--Congresses.