1. V. D. Shafranov and E. I. Yurchenko, Zh. Eksperim. Teor. Fiz.,53, 1157 (1967).
2. V. D. Shafranov, Zh. Tekh. Fiz.,30, 241 (1970).
3. S. V. Mirnov and I. B. Semenov, At. Energ.,30, 20 (1971).
4. A. I. Morozov and L. S. Solov'ev, Zh. Tekh. Fiz.,34, 1566 (1964).
5. P. K. C. Wang, Phys. Rev. Letters,24, 362 (1970).