1. Allen, M. S., McAllister, H. C., and Jefferies, J. T.: 1978, High Resolution Atlas of the Solar Spectrum 2678?2931 A, Inst. Astron., U. Hawaii, Honolulu, Hawaii, 58 pp.
2. Avrett, E. H.: 1992, in R. F. Donnelly (ed.), Proc. of the Workshop on the Solar Electromagnetic Radiation Study for Solar Cycle 22, Space Environment Lab., NOAA ERL, Boulder, Colo., 20.
3. Donnelly, R. F.: 1991, J. Geomagnet. Geoelectr. 43, Suppl., 835.
4. Fredga, K.: 1971, Solar Phys. 21, 60.
5. Hall, L. A., and Anderson, G. P.: 1988, Ann. Geophys. 6, 531.