1. A. Einstein:The Meaning of Relativity, Third Ed. (Princeton, N. J., 1950), p. 58.
2. For the three-dimensional analogue of the curve-geometry assumptions we use, seeD. Laugwitz:Differential and Riemannian Geometry, translated byF. Steinhardt, Sects.1 ·1 through1 ·4 (New York, 1965). Also see the discussion employing local pseudoorthonomical bases inJ. L. Synge:Relativity, The General Theory, Chap. I, Sect.3 (Amsterdam, 1960).
3. M. Riesz:Clifford Numbers and Spinors (Chaps. I-IV), Lecture Series No. 38 (College Park, Md., 1958), p. 180. See alsoS. Teitler:Phys. Rev. 159, 1073 (1967).
4. E. Schrödinger: Berlin. Ber. 105 (1932).
5. V. Bargmann: Berlin. Ber. 346 (1932).