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Luciano, Dennis; Gordon Prichett (January 1987). "Cryptology: From Caesar Ciphers to Public-Key Cryptosystems". The College Mathematics Journal. 18 (1): 2–17. CiteSeerX10.1.1.110.6123. doi:10.2307/2686311. JSTOR2686311.
Leighton, Albert C. (April 1969). "Secret Communication among the Greeks and Romans". Technology and Culture. 10 (2): 139–154. doi:10.2307/3101474. JSTOR3101474.
psu.edu
citeseerx.ist.psu.edu
Luciano, Dennis; Gordon Prichett (January 1987). "Cryptology: From Caesar Ciphers to Public-Key Cryptosystems". The College Mathematics Journal. 18 (1): 2–17. CiteSeerX10.1.1.110.6123. doi:10.2307/2686311. JSTOR2686311.