Columbia subject headings:
Artists' preparatory studies--Congresses.
Drawing--Conservation and restoration--Congresses.
Painting--Conservation and restoration--Congresses.
Painting--Expertising--Congresses.
Harvard subject headings:
Artists' preparatory studies--Congresses.
Infrared radiation--Congresses.
Painting--Expertising--Congresses.
Pictures--Copying--Congresses.
Princeton subject headings: