1. L. Lovasz, J. Pelikan, K. Vesztergombi,Discrete Mathematics, Elementary and Beyond, Springer, New York etc. 2000.
2. David M. Burton,Elementary Number Theory, Mc Graw Hill, Boston etc., 2002.
3. Joseph Kirtland,Identification Numbers and Check Digit Schemes, Math. Assoc. of America, 2001.
4. Thomas Koshy,Elementary Number Theory with Applications, Harcourt/Academic Press, 2002.
5. R. Hill,A First Course in Coding Theory, Clarendon Press, Oxford, 1986.