1. Athay, R. G.: 1976, The Solar Chromosphere and Corona: Quiet Sun, D. Reidel Publ. Co., Dordrecht, Holland, p. 406.
2. Chase, R. C., Krieger, A. S., ?vestka, Z., and Vaiana, G. S.: 1976, Space Res. 16, 917.
3. Cox, D. P. and Tucker, W. H.: 1969, Astrophys. J. 157, 1157.
4. Davis, J. M. and Krieger, A. S.: 1978, Bull. Am. Astron. Soc. 10, 439.
5. Davis, J. M. and Krieger, A. S.: 1982, Solar Phys., (in press).