1. E. Wigner, Phys. Rev.,40, 749 (1932).
2. G. Nienhuis, Physica,47, No. 3 425 (1970).
3. D. I. Blockintzev, J. Phys.,2, 71 (1940).
4. E. P. Bogdanov, V. L. Kon'kov, and V. N. Gorshenkov, Uch. Zap, GGPI, No. 98, 12 (1969).
5. A. A. Vlasov, Statistical Distribution Functions [in Russian], Nauka (1966).