Bennett, Ralph (1999) [1994], Behind the Battle: Intelligence in the War with Germany (Edisi Pimlico: New and Enlarged), London: Random House, ISBN0-7126-6521-8
Bertrand, Gustave (1973), Enigma ou la plus grande énigme de la guerre 1939–1945 (Enigma: The Greatest Enigma of the War of 1939–1945), Paris: Librairie Plon
Beesly, Patrick (1977), Very Special Intelligence: The Story of the Admiralty's Operational Intelligence Centre 1939–1945, Sphere Books Limited, ISBN0-7221-1539-3
Budiansky, Stephen (2000), Battle of wits: The Complete Story of Codebreaking in World War II, Free Press, ISBN978-0-684-85932-3 A short account of World War II cryptology which covers more than just the Enigma story.
Copeland, Jack (2004), "Enigma", dalam Copeland, B. Jack (ed.), The Essential Turing: Seminal Writings in Computing, Logic, Philosophy, Artificial Intelligence, and Artificial Life plus The Secrets of Enigma, Oxford: Oxford University Press, ISBN0-19-825080-0
Farago, Ladislas (1974) [1971], The game of the foxes: British and German intelligence operations and personalities which changed the course of the Second World War, Pan Books, ISBN978-0-330-23446-7 Has been criticised for inaccuracy and exaggeration
Hinsley, F. H.; Stripp, Alan, ed. (1993), Codebreakers: The inside story of Bletchley Park (Edisi OU Press paperback), Oxford: Oxford University Press, ISBN978-0-19-280132-6
Kahn, David (1997) [1967], The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet (Edisi 2nd Revised), New York: Simon & Schuster, ISBN978-0-684-83130-5
Kahn, David (29 December 1974), "Enigma Unwrapped: Review of F. W. Winterbotham's The Ultra Secret", New York Times Book Review, hlm. 5
Kozaczuk, Władysław (1984), Enigma: How the German Machine Cipher was Broken, and how it was Read by the Allies in World War Two, edited and translated by Christopher Kasparek [a revised and augmented translation of W kręgu enigmy, Warsaw, Książka i Wiedza, 1979, supplemented with appendices by Marian Rejewski, Frederick, MD, University Publications of America, ISBN978-0-89093-547-7 This is the standard reference on the crucial foundations laid by the Poles for World War II Enigma decryption.
Lewin, Ronald (2001) [1978], Ultra goes to War (Edisi Penguin Classic Military History), London: Penguin Group, ISBN978-0-14-139042-0 Focuses on the battle-field exploitation of Ultra material.
Mallmann-Showell, J.P. (2003), German Naval Code Breakers, Hersham, Surrey: Ian Allan Publishing, ISBN0-7110-2888-5, OCLC181448256
Pidgeon, Geoffrey (2003), The Secret Wireless War: The Story of MI6 Communications 1939–1945, St Leonards-on-Sea, East Sussex: UPSO Ltd, ISBN1-84375-252-2, OCLC56715513
Rejewski, Marian, wrote a number of papers on his 1932 break into Enigma and his subsequent work on the cipher, well into World War II, with his fellow mathematician-cryptologists, Jerzy Różycki and Henryk Zygalski. Most of Rejewski's papers appear in Kozaczuk 1984
Rejewski, Marian (1984), "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods: Appendix C", dalam Kozaczuk, Władysław; Kasparek, Christopher; Frederick, MD (ed.), Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two (Edisi 2), University Publications of America, hlm. 241–45, ISBN978-0-89093-547-7
Schlesinger, Arthur, Jr. (1992), "The London Operation: Recollections of a Historian", dalam Chalou, George C. (ed.), The Secrets War: The Office of Strategic Services in World War II, Washington, DC: Government Printing Office, ISBN978-0-911333-91-6 Pemeliharaan CS1: Banyak nama: authors list (link)
Smith, Michael (2007) [1998], Station X: The Codebreakers of Bletchley Park, Pan Grand Strategy Series (Edisi Pan Books), London: Pan McMillan Ltd, ISBN978-0-330-41929-1
Welchman, Gordon (1984) [1982], The Hut Six story: Breaking the Enigma codes, Harmondsworth, England: Penguin Books, ISBN0-14-00-5305-0 An early publication containing several misapprehensions that are corrected in an addendum in the 1997 edition.
Wilkinson, Patrick (1993), "Italian naval ciphers", dalam Hinsley, F.H.; Stripp, Alan (ed.), Codebreakers: The inside story of Bletchley Park, Oxford: Oxford University Press, ISBN978-0-19-280132-6
Winterbotham, F. W. (1974), The Ultra Secret, New York: Harper & Row, ISBN0-06-014678-8 The first published account of the previously secret wartime operation, concentrating mainly on distribution of intelligence. It was written from memory and has been shown by subsequent authors, who had access to official records, to contain some inaccuracies.