1. Allen, C. W.: 1973,Astrophysical Quantities, 3rd Edn., Univ. of London, The Athlone Press, London.
2. Beals, C. S.: 1950,Publ. of the Dominion Astrophys. Obs. 9, 1.
3. Beigman, I. L., Vajnshtejn, L. A., Klimuk, P. I., Mandal'shtam, S. L., Sevost'yanov, V. I., Tindo, I. P., and Shurygin, A. I.: 1976,Pis'ma b AZh (Letter to AJ) 2, 18.
4. Bleeker, J. A. M., Deerenberg, A. J. M., Heise, J., Yamashita, K., and Tanaka, Y.: 1973,Nature Phys. Sci. 241, 55.
5. Boggende, A. J. F. den, and Lafleur, H. Th. J. A.: 1975,I.E.E.E. Trans. on Nucl. Sci. 22, 555.