1. Nathan Altshiller-Court,College Geometry, 2nd edition, Barnes & Noble Books, New York, 1952.
2. Nathan Altshiller-Court,Modern Pure Solid Geometry, Macmillan Publishing Co., New York, 1935.
3. On the De Longchamps Circle of the Triangle
4. E3155
5. George S. Carr,Formulas and Theorems in Pure Mathematics, 2nd edition, Chelsea, 1970.