1. 1. Neubauer, F. M. et al. Nature 321, 352–355, 1986. 2. Reme, H. et al. Nature 321, 349–352, 1986. 3. Johnstone, A. et al Nature 321, 344–347, 1986. 4. Balsiger, H. et al. Nature 321, 330–334, 1986. 5. Formisano, V. et al. Adv. Space Res. 6, 229–233, 1986. 6. Coates, A. J. et al. The Exploration of Halley's comet Vol. 1 (eds Battrick, B., Rolfe, E. J. & Reinhard, R.) 263–268 (ESASP–250, Paris, 1986). 7. Wilken, B. et al. The Exploration of Halley's comet Vol. 1 (eds Battrick, B., Rolfe, E. J. & Reinhard, R.) 305–308 (ESASP–250, Paris, 1986). 8. Anderson, K. A. et al. The Exploration of Halley's comet Vol. 1 (eds Battrick, B., Rolfe, E. J. & Reinhard, R.) 259–261 (ESASP–250, Paris, 1986). 9. Johnstone, A. D. et al. The Giotto mission—its Scientific Investigations (eds Reinhard, R. & Battrick, B.) 15–32 (ESASP–1077, Noordwijk, 1986). 10. Reme, H. et al. The Giotto mission—its Scientific Investigations (eds Reinhard, R. & Battrick, B.) 33–52 (ESASP–1077, Noordwijk, 1986). 11. Johnstone, A. D. el al. IEEE Trans. Nucl Sci. NS–32, 139–144, 1985. 12. Wilken, B. et al. J. Phys. E (submitted). 13. Carbon, C. W. et al Adv. Space Res. 2, 67–70 (1982). 14. Bame, S. J. et al. Science 232, 356–361 (1986). 15. Hynds, R. J. et al Science 232, 361–365 (1986). 16. Smith, E. J. et al The Exploration ofHalley's comet Vol. 3 (eds Battrick, B., Rolfe, E. J. & Reinhard, R.) 461–465 (ESASP–250, Paris, 1986). 17. Anderson, K. A. et al. Geophys. Res. Lett, (submitted). 18. Wilken, B. et al Astr. Astrophys. (submitted). 19. Omidi, N. & Winske, D. Eos 67, 1144 (1986). 20. Axford, W. I. Proc. 17th Int. Cosmic Ray Conf 12, 155–203 (Service de Doc. du CEN, Saclay, 1981). 21. Drury, L.O'C. Rep. Prog. Phys. 46, 973–1027 (1983).