References
- Hilton, P. and Pedersen, J., The Euler characteristic and Polya's dream, Amer. Math. Monthly 103(1996), 121-131. https://doi.org/10.2307/2975104
- Hopf, H., Differential Geometry in the Large, Springer-Verlag, Berlin, 1983.
- Pak, C. R., Kim, S.-B., Kim, D.-S. and Cho, K. I., Are there any numbers other than the Euler number for polyhedra? (Korean), Comm. Korean Math. Soc. 15 (2000), no. 4, 669-674.
- Polya, G., Mathematical Discovery, Combined Edition, John Wiley and Sons, Inc., New York, 1981.