1. Axisa, F., Avignon, Y., Martres, M. J., Pick, M., and Simon, P.: 1971, Solar Phys. 19, 110.
2. Axisa, F., Martres, M. J., Pick, M., and Soru-Escaut, I.: 1972, in preparation.
3. Daigne, G., Lantos-Jarry, M. F., and Pick, M.: 1971, in R. Howard (ed.), ?Solar Magnetic Fields?, IAU Symposium 43, Reidel, Dordrecht, p. 367.
4. De Groot, T. and Van Nieuwkoop, J.: 1968, Solar Phys. 4, 332.
5. De Jager, C.: 1969, in C. de Jager and Z. ?vestka (eds.), Solar Flares and Space Research, North-Holland Publ. Co., Amsterdam, p. 1.