1. H. F. Baker, Introduction to Plane Geometry, Cambridge University Press, London, 1943.
2. O. Bottema, Hoofdstukken uit de Elementaire Meetkunde, N. V. Servire, The Hague, 1944.
3. W. K. Clifford, Collected Mathematical Papers, Macmillan, London, 1882.
4. J. Coolidge, Treatise on the Circle and the Sphere, Oxford University Press, London, 1916.
5. H. S. M. Coxeter, Introduction to Geometry, 2nd ed., Wiley, New York, 1969.