1. Adams, J. and Pneuman, G. W.: 1976, Solar Phys. 46, 185.
2. Altschuler, M. D., Levine, R. H., Stix, M., and Harvey, J.: 1977, Solar Phys. 51, 345.
3. Behannon, K. W.: 1976, in D. J. Williams (ed.), Physics of Solar Planetary Environments, Am. Geophys. Union, p. 332.
4. Boischot, A.: 1957, Compt. Rend. Acad. Sci. Paris 245, 2194.
5. Cohen, M. H.: 1961, Astrophys. J. 133, 978.