1. Einstein, A. (1918).Ann. Physik (Leipzig),55, 241.
2. See, for example, the discussion in Anderson, J. L. and Gautreau, R. (1969)Phys. Rev.,185, No. 5, 1656.
3. Kretschmann, E. (1917)Ann. Physik (Leipzig),53, 575.
4. Fock, V. (1964).The Theory of Space, Time, and Gravitation, Pergamon Press, Oxford.
5. Einstein, A. (1955)The Meaning of Relativity. Princeton University Press, Princeton, p. 100.