Columbia subject headings:
Communism--Soviet Union--History.
Fourth International.
Trotsky, Leon, 1879-1940.
Harvard subject headings:
Communism--Soviet Union--History
Fourth International.
Trotsky, Leon, 1879-1940
Princeton subject headings:
Communism--Soviet Union--History.
Fourth International.
Trotsky, Leon, 1879-1940.