1. Abramowitz, M. and Stegun, I. A.: 1965, Handbook of Mathematical Functions, Dover Publ., New York, p. 417.
2. Burton, W. M.: 1967, Culham Laboratory Memorandum, CLM-M66.
3. Burton, W. M.: 1969, Solar Phys. 8, 53.
4. Gradshteyn, I. S. and Ryzhik, I. M.: 1965, Tables of Integrals, Series and Products, Academic Press, New York, p. 316, Formula 3.366 (2).
5. Pounds, K. A. and Russell, P. C.: 1966 in Space Research, Vol. VI (ed. by Smith-Rose), Spartan Books, New York, p. 38.