1. Bravo, S.: 1993,Adv. Space Res. 13(9), 371.
2. Bravo, S.: 1994,Geofis. Int. 33, 333.
3. Bravo, S. and Nikiforova, E.: 1994,Solar Phys. 151, 333.
4. Bravo, S. and Lanzagorta, M.: 1994, in D. N. Baker, V. O. Papitashvili, and M. J. Teague (eds.), Solar Terrestrial Energy Program, Proceedings of the 1992 STEP Symposium/5th COSPAR Colloquium, Pergamon, London, p. 227.
5. Bravo, S. and Pérez-Enríquez, R. 1994,Rev. Mex. Astron. Astrofis. 38, 17.