Columbia subject headings:
Fourth International.
Soviet Union. Obʺedinennoe gosudarstvennoe politicheskoe upravlenie.
Trotsky, Leon, 1879-1940--Assassination.
Harvard subject headings:
Fourth International.
Soviet Union. Obʺedinennoe gosudarstvennoe politicheskoe upravlenie.
Trotsky, Leon, 1879-1940--Assassination.
Princeton subject headings: