Columbia subject headings:
Espionage, Soviet--United States--History--20th century.
Spies--Soviet Union.
Spies--United States.
United States--History--1933-1945.
Harvard subject headings:
Espionage, Soviet--United States--History--20th century.
Espionage, Soviet--United States--History.
Spies--Soviet Union.
Spies--United States
United States--History--1933-1945.
Princeton subject headings:
Espionage, Soviet--United States--History--20th century.
Spies--Soviet Union.
Spies--United States.
United States--History--1933-1945.