1. Proceedings of the “Ettore Majorana” International School of Mathematical Physics, Erice 1977, edited by G. Velo, A. S. Wightman, Lecture Notes in Physics vol. 73, Springer-Verlag, Berlin-Heidelberg-New York, 1978.
2. Majorana E., Nuovo Cimento9 (1932), 335.
3. Bhabha H.J., Harish-Chandra, Proc. Roy. Soc.A192 (1947), 195;Harish-Chandra, Phys. Rev.71 (1947), 793;Wild E., Proc. Roy. Soc.A191 (1947), 253; see also referencesin [1] p. 20.
4. Frank V., Nucl. Phys.B59 (1973), 429;Cox W., J. Phys. A: Math. Nucl. Gen.7 (1974) 1; 665; 2248;Fedorov F. I.,Pletyuchov V. A., Izv. AN SSSR6 (1974), 63;Hurley W. J.,Sudarshan E. G., Ann. Phys. (N. Y.) 55 (1974), 546;Bracken A. J., J. Phys. A: Math. Nucl. Gen.8 (1975), 800.
5. Garding L., Medd. Lunds Mat. Sem.6 (1944), 1.