Columbia subject headings:
Espionage, German--Great Britain--History--20th century.
Fascists--Great Britain--History--20th century.
Subversive activities--Great Britain--History--20th century.
World War, 1939-1945--Secret service--Great Britain.
Harvard subject headings:
Espionage, German--Great Britain--History--20th century.
Fascists--Great Britain--History--20th century.
Subversive activities--Great Britain--History--20th century.
World War, 1939-1945--Secret service--Great Britain.
Princeton subject headings:
Espionage, German--Great Britain--History--20th century.
Fascists--Great Britain--History--20th century.
Subversive activities--Great Britain--History--20th century.
World War, 1939-1945--Secret service--Great Britain.