1. Adler, R., Bazin, M., and Schiffer, M. (1965).Introduction to General Relativity, McGraw Hill, New York.
2. Apostol, T. (1963).Mathematical Analysis, Addison Wesley, Reading, Massachusetts.
3. Frechet, M. (1925).Fund. Math.,7, 210.
4. Geroch, R. (1971). ?Spacetime structure from a global viewpoint,? inGeneral Relativity and Cosmology, Proceedings of the International Summer School in Physics ?Enrico Fermi,? course XLVII, ed. Sachs, R., Academic Press, New York pp. 71?103.
5. Geroch, R. (1970).J. Math. Phys.,11, 437.