References
- Hilbert, D. & Cohn-Vossen, S.: Geometry and the imagination, Translated by P. Nemenyi. Chelsea Publishing Company, New York, N. Y., 1952.
- Kim, Y. H.: Characterization of generalized surfaces of revolution. Nihonkai Math. J. 2 (1991), 63-69.
- O'Neill, B.: Elementary diffenrential geometry, 2nd edition. Academic Press, 1997.