Columbia subject headings:
Labor--Soviet Union--History--Congresses.
Soviet Union--Economic conditions--1917-1945--Congresses.
Harvard subject headings:
Soviet Union--Economic conditions--1917-1945--Congresses.
Working class--Soviet Union--History--Congresses.
Princeton subject headings:
Labor--Soviet Union--History--20th century--Congresses.
Soviet Union--Ethnic relations--Congresses.