1. Adams, N. G., Smith, D. and Clary, D. C. 1985, Ap. J. Letts, 296, 131.
2. Adams, N. G., Smith, D. and Millar, T. J. 1984, MNRAS, 211, 857.
3. Anicich, V. G. and Huntress, W. T. 1986, Ap. J. Suppl, 62, 553.
4. Bardsley, J. N. 1968, J. Phys. B, 1, 365.
5. Barlow, S. E., Dunn, G. H. and Schauer, M. 1984, Phys. Rev. Lett, 52, 903 and 53, L1610.