Columbia subject headings:
Communism--Soviet Union.
Proletariat.
Soviet Union--History--Revolution, 1917-1921.
Harvard subject headings:
Communism--Soviet Union
Proletariat.
Soviet Union--History--Revolution, 1917-1921.
Princeton subject headings:
Communism--Soviet Union.
Proletariat.
Soviet Union--History--Revolution, 1917-1921.