1. William P. Bundy, "From the Depths to the Heights," Cryptologia, 6 (January 1982), 64 73.

2. House of Commons Debates, 941 (January 12, 1978), cols. 829 830.

3. On the cryptanalysis of Enigma, see Marian Rejewski, "Mathematical Solution of the Enigma Cipher," Cryptologia, 6 (1982): 1 18; the appendix by Tadeusz Lisicki in Jozef Garlinski, Intercept: The Enigma War (London, 1979); Gordon Welchman, The Hut Six Story: Breaking the Enigma Codes (New York, 1982).

On the breaking of Geheimschreiber by GC&CS, see Welchman, 176 179; Brian Johnson, The Secret War (London, 1978), 338 347.

4. For a fascinating and well written autobiographical account of the RAF's Y Service, see Aileen Clayton, The Enemy is Listening (London, 1980).

5. See Alfred J. Price, Instruments of Darkness. (London, 1977).

6. Welchman states that, even as late as 1944, similar difficulties made it impossible for the United States Army and Navy cryptanalytic divisions to discuss Enigma topics with each other directly although they wanted to do so. The British acted as a go-between: Welchman, 74, 75.

7. A Soviet intelligence net in Switzerland that is alleged to have provided quantities of valuable intelligence. Its sources have never been discovered. See further, Garlinski, 107 118; Pierre Accoce and Pierre 'Acquet, The Lucy Ring (London, 1967).

8. J rgen Rohwer, "Ultra and the Battle of the Atlantic. The German View," Presentation in 1977 to the U. S. Naval Academy, 12. [Cited in Volume II.]

9. On this machine,...