Columbia subject headings:
Espionage, American--History--Dictionaries.
Espionage--United States--History--Dictionaries.
Harvard subject headings:
Espionage, American--History--Encyclopedias.
Espionage--United States--History--Encyclopedias.
Princeton subject headings:
Espionage, American--History--Dictionaries.
Espionage--United States--History--Dictionaries.