Original Documents from the British Admiralty, Room 40, regarding the Zimmermann-/Mexico Telegram: Photocopies from theThe National Archives, Kew, Richmond
also Vol. 1-3 in an English translation: The submarine war against commerce. 1966 [1932]. Beesly, Patrick. Room 40: British Naval Intelligence 1914-1918
also Vol. 1-3 in an English translation: The submarine war against commerce. 1966 [1932]. Beesly, Patrick. Room 40: British Naval Intelligence 1914-1918