Columbia subject headings:
Espionage--Switzerland--History--20th century.
Secret service--Switzerland--History--20th century.
Switzerland--History--20th century.
World War, 1914-1918--Secret service--Switzerland.
World War, 1914-1918--Switzerland--Propaganda.
Harvard subject headings:
Espionage--Switzerland--History--20th century.
Secret service--Switzerland--History--20th century.
Switzerland--History--20th century.
World War, 1914-1918--Secret service--Switzerland.
World War, 1914-1918--Switzerland--Propaganda.
Princeton subject headings:
Espionage--Switzerland--History--20th century.
Secret service--Switzerland--History--20th century.
Switzerland--History--20th century.
World War, 1914-1918--Propaganda--Switzerland.
World War, 1914-1918--Secret service--Switzerland.