Ratcliff, R. A. (2004). "How statistics led the Germans to believe Enigma secure and why they were wrong:Neglecting the practical mathematics of cipher machines". Cryptologia. 27 (2): 119–131. doi:10.1080/0161-110391891801. ISSN0161-1194. S2CID41982133.
Ratcliff, R. A. (2004). "How statistics led the Germans to believe Enigma secure and why they were wrong:Neglecting the practical mathematics of cipher machines". Cryptologia. 27 (2): 119–131. doi:10.1080/0161-110391891801. ISSN0161-1194. S2CID41982133.
Ratcliff, R. A. (2004). "How statistics led the Germans to believe Enigma secure and why they were wrong:Neglecting the practical mathematics of cipher machines". Cryptologia. 27 (2): 119–131. doi:10.1080/0161-110391891801. ISSN0161-1194. S2CID41982133.