1. A. Einstein, The Meaning of Relativity (Methuen, UK, 1922)
2. C.S. Unnikrishnan, Physics in the ‘once-given’ Universe, in Recent Developments in Theoretical Physics. ed. by S. Ghosh, G. Kar (World Scientific, Singapore, 2009), pp.99–120
3. C.S. Unnikrishnan, A new gravitational paradigm for relativity and dynamics. J. Phys. (Conf. Ser.) 1466, 012007 (2020)
4. A. Einstein, Theoretical comments on the superconductivity of metals. Translated in The Collected Papers of Albert Einstein, vol. 13, Doc. 76 (Princeton University Press, 1922)
5. E. Mach, The Science of Mechanics, 4th edn. (The Open Court Publishing Co., London, 1919), pp. 222–245 and appendix XX