1. Gibson, E. G.: 1973, The Quiet Sun, NASA SP-303.
2. Hoel, P. G.: 1954, Introduction to Mathematical Statistics, J. Wiley and Sons, Inc., New York, p. 297.
3. Houtgast, J.: 1965, Koninkl. Nederl. Akad. van Wetenschappen Proc. B
68, No. 5.
4. Krat, V. A., Makarov, V. I., and Tavastsherna, K. S.: 1980, Solar Phys.
68, 237.
5. Labs, D. and Neckel, H.: 1968, Z. Astrophys.
69, 1.