1. H. Beker and F. Piper, Cipher Systems, London: Northwood Books, 1982.
2. P. Elias, Interval and recency rank source coding: Two on-line adaptive variable-length schemes, IEEE Trans. Inform. Theory, vol. IT-33, pp. 3–10, Jan. 1987.
3. W. Feller, An Introduction to Probability Theory and its Applications, third ed., vol. 1, New York, NY: Wiley, 1968.
4. D.E. Knuth, The art of computer programming, vol. 2, 2nd edition, Reading, MA: Addison-Wesley, 1981.
5. R.A. Rueppel, Analysis and Design of Stream Ciphers, New York, NY: Springer, 1986.