
REFERENCES

K. Appel and W. Haken, Every planar map is four colorable. I. Discharging. Illinois J. Math. 21 (1977), 429490.
K. Appel and W. Haken, Every planar map is four colorable. II. Reducibility. Illinois J. Math. 21 (1977), 491567.
K. Appel and W. Haken, Every planar map is four colorable. With the collaboration of J. Koch. Contemporary Mathematics, 98. American Mathematical Society, Providence, RI, 1989. xvi+741 pp. ISBN: 0821851039.
K. Appel and W. Haken, "The FourColor Problem" in Mathematics Today (L. A. Steen editor), Springer NY 1978.
K. Appel and W. Haken, "The FourColor proof suffices", Mathematical Intelligencer 8 no.1 pp. 1020 1986.
K. Appel and W. Haken, "The Solution of the FourColor Map Problem", Scientific American vol. 237 no.4 pp. 108121 1977.
D. Barnett, Map coloring, Polyhedra and The FourColor Problem, Dolciani Math. Expositions No. 8, Math. Asso. of Amer., Washington DC 1984.
J. H. Cadwell, Topics in Recreational Mathematics, Chapter 8 pp. 7687 Cambridge Univ. Press 1966.
K. J. Devlin, All The Math That's Fit To Print, Chap. 17; 67 pp. 468; 1612 MAA Washington DC 1994.
K. J. Devlin, Mathematics: The New Golden Age, Chapter 7, Columbia Univ. Press NY 1999.
M. Gardner, New Mathematical Diversions, Chapter 10 pp. 113123, Math. Assoc. of Amer. Washington DC 1995.
J. L. Gross and T. W. Tucker, Topological Graph Theory, Wiley, 1987; see Table 5.1 p. 221.
M. E. Lines, Think of a Number, Chapter 10 pp. 91100 Institute of Physics Pub. London 1990.
G. Ringel and J. W. T. Youngs, Solution of the Heawood mapcoloring problem, Proc. Nat. Acad. Sci. USA, 60 (1968), 438445.
Robertson, N.; Sanders, D.; Seymour, P. and Thomas, R., The fourcolor theorem. J. Combin. Theory Ser. B 70 (1997), no. 1, 244.
Robertson, N.; Sanders, D. P.; Seymour, P. and Thomas, R., A new proof of the fourcolor theorem. Electron. Res. Announc. Amer. Math. Soc. 2 (1996), no. 1, 1725.
W. W. Rouse Ball & H. S. M. Coxeter, Mathematical Recreations and Essays, Chapter VIII pp. 222242 Dover NY 1987.
W. L. Schaaf, Recreational Mathematics. A guide to the literature, Chapter 4.7 pp. 746 NCTM Washington DC 1963.
W. L. Schaaf, A Bibliography of Recreational Mathematics Vol. 2, Chapter 4.6 pp. 759 NCTM Washington DC 1972.
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).
I. Stewart, From Here to Infinity, Chapter 8 pp. 104112, Oxford Univ.Press 1996.
H. Tietze, Famous Problems of Mathematics, Chapter XI pp. 226242 Graylock Press Baltimore MD 1966.
Stan Wagon, Mathematica In Action, W.H. Freeman and Company, NY, 1991, pages 232  237.
R. Wilson, Four Colors Suffice, Princeton Univ. Press, 2002.
