1. Einstein, A. (1905).Ann. Phys. (Leipzig) 17, 891.
2. Robertson, H. P. (1949).Rev. Mod. Phys. 21, 378.
3. Reichenbach, H. (1958).The Philosophy of Space and Time (Dover Publications, Inc., New York).
4. Grunbaum, A. (1960). InPhilosophy of Science, A. Danto and S. Morgenbesser, eds. (Meridian Books, New York).
5. Ruderfer, M. (1960).Proc. IRE 48, 1661.