1. M. J. Seaton, J. Atmos. Terr. Phys. 4, 285 (1954).
2. National Bureau of Standards Data Series;WL Wiese,1966
3. L. Vegard, in Terrestrial Magnetism and Electricity, J. A. Fleming, Ed., Mraw-Hill, New York, 1939, Chap. 11.
4. S. Chapman, Proc. R. Soc. Lond. Ser. A 132, 353 (1931).
5. A. Omholt, The Optical Aurora, Springer-Verlag, Berlin, 1971, Sections 2.2 and 4.2.2.