1. Huebner, W.F.: see Proceeding [i] p. 1.
2. Huebner, W.F., McKay, Ch.P.: see Proceeding [i] p. 305.
3. Festou, M.C., Rickman, H., West, R.M.: Astronomy Astrophys. Review 4 (1993) 363.
4. Whipple, F.L.: see Proceeding [a] p. 1259.
5. Comets in the Post-Halley Era, (Newburn, R.L., Neugebauer, M., Rahe, J., eds.). Dordrecht, The Netherlands: Kluver Academic Publishers (1991).