Columbia subject headings:
Harvard subject headings:
Military intelligence--Poland--History--20th century.
Poland--History--Wars of 1918-1921--Cryptography.
Poland--History--Wars of 1918-1921--Military intelligence.
Radio, Military--Poland--History--20th century.
Telegraph, Wireless--Poland--History--20th century.
Princeton subject headings:
Poland--History--1918-1945.
Radio broadcasting--Poland--History.
Russo-Polish War, 1919-1920.