1. We quote a few experimental papers on this subject:R. V. Ambartsumyan, N. G. Basoy, V. A. Bo $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{I} $$ ko, V. S. Zuev, O. N. Krokhin, P. G. Krynkov, Yu. V. Senatski $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{I} $$ andYu. Yu. Sto $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{I} $$ lov:Soc. Phys. JETP,21, 1061 (1965);
2. A. Ducauze, G. Tonon andP. Veyrie:Compt. Rend.,261, 4039 (1965);
3. P. Nelson:Journ. de Phys.,26, 476 (1965);A. F. Haught andD. H. Polk:Proceedings of the Culham Conference on Plasma Physics and Controlled Nuclear Fusion Research, 6–10 September 1965, vol.2 (Vienna, 1966), p. 953;U. Ascoli-Bartoll, C. De Michelis andF. Mazzucato: same proceedings, vol.2, p. 941;E. W. Sucov,et al.:Magnetic confinement of laser-produced plasmas. Westinghouse Report 65-IE2-PLASL-R1.
4. J. M. Dawson:Phys. Fluids,7, 981 (1964);
5. N. G. Basov andO. N. Krokhin:Sov. Phys. JETP,19, 123 (1964);