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2. J. H. Cadwell, Topics in Recreational Mathematics, Cambridge University Press, New York, 1966.
3. H. S. M. Coxeter, Introduction to Geometry, Wiley, New York, 1961, 1969.
4. H. S. M. Coxeter and W. O. J. Moser, Generators and Relations for Discrete Groups, Springer-Verlag, New York, 1957, 1965.