References

1: D.R. Cox and H.D. Miller The Theory of Stochastic processes Methuen, London 1965
2: M. Gardner Penrose Tiles to Trapdoor Ciphers Freeman and company 1989
3: M. Gardner, 1978, Mathematical Games, Scientific American, 238, No. 2, February, 19-32.
4: J. C. Lagarias and R. J. Vanderbei, 1988, The Kruskal Count, AT&T Bell Laboratories, Murray Hill, New Jersey 07974