Columbia subject headings:
Communists--Soviet Union--History.
Soviet Union--History--Revolution, 1917-1921--Atrocities.
Harvard subject headings:
Communists--Soviet Union--History--Sources.
Soviet Union--History--Revolution, 1917-1921--Atrocities--Sources.
Princeton subject headings:
Communists--Soviet Union--History--Sources.
Soviet Union--History--Revolution, 1917-1921--Atrocities--Sources.