1. I. G. Galilei, Dialogo. Opere. VIL, p 299, Edizione nazionale Florence (1890–1909).
2. E. P. Wigner, Annals Math. 40, 139 (1939).
3. A. Einstein, Annalen der Physik 17, 891 (1905).
4. H. Minkowski, Göttinger Nachr. (1908), p. 53; see also his Address delivered at the 80th Assembly of German Natural Scientists and Physicians, at Cologne, September 1908, reprinted in the well-known Dover paperback The Principle of Relativity. The quotation on page 73 is taken from this address.
5. P. G. Roll, R. Krotkov, and R. H. Dicke, Ann. Phys. (N.Y.) 26, 442 (1964); V. B. Braginsky and V. J. Panov, Zh. Eksp. Teor. Fiz. 61, 875 (1971).