See A. Einstein, The Meaning of Relativity (6th ed. 1956) and, with others, The Principle of Relativity (1923, repr. 1958; a collection of original papers on the theory); M. Gardner, Relativity for the Million (1962); D. Bohm, The Special Theory of Relativity (1965); J. Schwinger, Einstein's Legacy (1986).
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.