Columbia subject headings:
Collectors' marks--Europe--Congresses.
Drawing, European--Congresses.
Drawing--Collectors and collecting--Europe--History--Congresses.
Drawing--Private collections--Europe--Congresses.
Harvard subject headings:
Collectors' marks--Europe--Congresses.
Drawing, European--Congresses.
Drawing--Collectors and collecting--Europe--History--Congresses.
Drawing--Private collections--Europe--Congresses.
Princeton subject headings: