Columbia subject headings:
Harvard subject headings:
Art dealers--Germany--Biography.
Art dealers--Germany--Correspondence.
Gretor, Willy, 1868-1923--Correspondence.
Gretor, Willy, 1868-1923.
Princeton subject headings:
Art dealers--Germany--Correspondence.
Gretor, Willy, 1868-1923--Correspondence.
Gretor, Willy, 1868-1923.