
REFERENCES

A. de Vries, Formal Languages: An Introduction, http://haegar.fhswf.de/Seminare/Genome/Archiv/languages.pdf
Andreas Distler and Tom Kelsey, The Monoids of Order Eight and Nine, in Intelligent Computer Mathematics, Lecture Notes in Computer Science, Volume 5144/2008, SpringerVerlag. [From N. J. A. Sloane, Jul 10 2009]
G. E. Forsythe, SWAC computes 126 distinct semigroups of order 4, Proc. Amer. Math. Soc. 6, (1955). 443447.
H. Juergensen and P. Wick, Die Halbgruppen von Ordnungen <= 7, Semigroup Forum, 14 (1977), 6979.
D. J. Kleitman, B. L. Rothschild and J. H. Spencer, The number of semigroups of order n, Proc. Amer. Math. Soc., 55 (1976), 227232.
R. J. Plemmons, There are 15973 semigroups of order 6, Math. Algor., 2 (1967), 217; 3 (1968), 23.
Satoh, S.; Yama, K.; and Tokizawa, M., Semigroups of order 8, Semigroup Forum 49 (1994), 729.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
