Altwegg, K., Balsiger, H., Geiss, J., Goldstein, R., Ip, W.-H., Meier, A., Neugebauer, M., Rosenbauer, H., & Shelley, E. (1993). The ion population between 1300 km and 230 000 km in the coma of comet P/Halley. Astronomy and Astrophysics, 279, 260-266.