1. Beckers, J. M.: 1976, in D. J. Williams (ed.), Physics of Solar Planetary Environments, Publ. By AGU, p. 89.
2. Foukal, P. V.: 1975, Solar Phys. 43, 327.
3. Galeev, A. A. and Sagdeev, R. S.: 1979, Rev. Plasma Phys. 7.
4. Howard, R. and Švestka, Z.: 1977, Solar Phys. 54, 65.
5. Levine, R. H. and Withbroe, G. L.: 1977, Solar Phys. 51, 83.