1. Drever, R. W. P. (1961).Phil. Mag.,6, 683.
2. Eddington, A. S. (1924).The Mathematical Theory of Relaticity, 2nd ed., p. 93, Cambridge University Press.
3. Einstein, A. (1916).Ann. d. Physik,49, 769.
4. Einstein, A (1950).The Meaning of Relativity, 3rd. ed., Princeton University Press.
5. Partridge, R. B. and Wilkinson, D. T. (1967).Phys. Rev. Lett.,18, 557.