References
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- Clark, R. 1977. The man who broke purple: The life of Colonel William F. Friedman, who deciphered the Japanese code in World War II. Boston, MA: Little Brown.
- Dooley, J. 2016. Codes, ciphers, and spies. New York, NY: Springer.
- Friedman, W. 1922. The index of coincidence and its applications in cryptography. Paris, France: Imprimerie-Librairie Militaire Universelle.
- Friedman, W., and E. Friedman. 1957. The Shakespearean ciphers examined: An analysis of cryptographic systems used as evidence that some author other than William Shakespeare wrote the plays commonly attributed to him. Cambridge, UK: Cambridge University Press.
- Hitt, P. 1916. Manual for the solution of military ciphers. Fort Leavenworth, KS: The Army Service Schools Press.
- Mauborgne, J. 1914. An advanced problem in cryptography and its solution. Fort Leavenworth, KS: The Army Service Schools Press.
- Yardley, H. 1931. The American black chamber. Indianapolis, IN: Bobbs-Merrill.