1. Birn, J.: 1980, Proc. CECAM workshop ?Solar Flares?, held in Orsay, 1979, p.3.
2. Birn, J., Goldstein, H., and Schindler, K.: 1978, Solar Phys. 57, 81.
3. Heyvaerts, J., Lasry, J. M., Schatzman, M., and Witomsky, P.: 1978, in E. Jensen, P. Maltby, and F. Q. Orrall (eds.), ?Physics of Solar Prominences?, IAU Colloq. 44, 174.
4. Heyvaerts, J., Lasry, J. M., Schatzman, M., and Witomsky, P.: 1979, ?Blowing Up of Force Free Magnetic Configurations?, preprint, Univ. de Paris-Nord.
5. Kippenhahn, R. and Schl�ter, A.: 1957, Z. Astrophys. 43, 36.