Columbia subject headings:
Communists--Soviet Union--Correspondence.
Lenin, Vladimir Ilʹich, 1870-1924--Correspondence.
Revolutionaries--Soviet Union--Correspondence.
Harvard subject headings:
Communists--Soviet Union--Correspondence.
Lenin, Vladimir Ilʹich, 1870-1924--Correspondence.
Revolutionaries--Soviet Union--Correspondence
Princeton subject headings:
Labor leaders--Germany--Correspondence.
Labor movement--Germany--Sources.
Lenin, Vladimir Ilʹich, 1870-1924--Correspondence.
Revolutionaries--Soviet Union--Correspondence.