1. S. Schlieder:Zeits. f. Naturf.,15 a, 448 (1960).
2. L. Castell:Zeits. f. Naturf.,20 a, 737 (1965).
3. E. Majorana:Nuovo Cimento,9, 335 (1932).
4. J. M. Gel'fand, R. A. Minlos andZ. Ya. Shapiro:Representations of the rotation and Lorentz groups and their applications (London, 1963).
5. J. B. Ehrman:Proc. Camb. Phil. Soc.,53, 290 (1957);N. T. Evans:J. Math. Phys. 8, 170 (1967);R. Raczka, N. Limić andJ. Niederle:J. Math. Phys.,7, 1861, 2026 (1966).