Magill, J. and Galy, J. (2005) Radioactivity and radionuclide’s. Institute for Trans-Uranium Elements, 32(5), 254-260.
 Lawden, F. and Derek (1982) An introduction to tensor calculus and relativity. John Wiley and Sons, New York.
 Martin, R. (2006) Nuclear and particle physics. University College London, London.
 Weinberg, S. (1972) Gravitation and cosmology. John Wiley and sons, New York.
 Mubarak, D.A. and Ali, T. (2003) The special relativity in the presence of Gravitation and Other Field. U of K, Khartoum.
 Adler, R., Basin, M. and Shifter, M. (1975) Introduction to general relativity. MC Graw Hill Book Company, Tokyo.