1. Kac V. C., Adv. Math.26 (1977), 8.
2. Green H. S., Phys. Rev.90 (1953), 270.
3. Greenberg O. W., Messiah A. M., Phys. Rev.138 (1965), 1155.
4. Palev T., Ann. Inst. Henri Poincaré23 (1975), 49.
5. Palev T., Thesis, Institute for Nuclear Research and Nuclear Energy, Sofia, 1976; for theA-statistics see also Preprint JINR, E 17-10550 (1977).