Columbia subject headings:
Soviet Union--History--Revolution, 1917-1921--Influence--Congresses.
Harvard subject headings:
Communism and international relations--Congresses.
Communism--1945---Congresses.
Soviet Union--History--Revolution, 1917-1921--Influence--Congresses.
Princeton subject headings:
Soviet Union--History--Revolution, 1917-1921--Congresses.
World politics--20th century.