1. Armstrong, J.W., Cordes, J.M., Rickett, B.J. 1981, Nature, 291, 561.
2. Arnaud, K., et al. 1982, M.N.R.A.F., 201, 745.
3. Arnaud, M., and Cassé, M. 1985, Astr. Ap., 144, 64.
4. Axford, W.I., Leer, E., Skandron, K.G. 1977, Proc. 15th Int. Cosmic Ray Canf., 11, 132.
5. Axford, W.I. 1981; in Origin of Cosmic Rays, IAU Symp. 94, Reidel, p. 339