1. Allen, C. W.: 1963, Astrophysical Quantities, Second Edition, University of London, The Athlone Press, London.
2. Argo, H. V., Bergey, J. A., and Evans, W. D.: 1970, Astrophys. J. 160, 283 (Ref. 1).
3. Athay, R. G.: 1971, in C. J. Macris (ed.), Physics of the Solar Corona, Reidel Publ. Co., Dordrecht, p. 36.
4. Austin, W. E., Purcell, J. D., Tousey, R., and Widing, K. G.: 1966, Astrophys. J. 145, 373 (Ref. 2).
5. Bates, D. R. and Damgaard, A.: 1949, Phil. Trans. Roy. Soc. (London) 242, 101.