1. Anisimov, S.I.: 1958, Soviet Phys. JETP
27, 321
2. Ashkenas, H., Sherman, F. S.: 1966, IVth Rarefield Gas Dynamics Symposium, ed. J. H. de Leeuw, Academic Press, NY, Vol. 2, p. 84
3. Bockelée-Morvan, D.: 1987, Astron. Astrophys.
181, 169
4. Bockelée-Morvan, D., Crovisier, J.: 1987, in: Proceedings of the International Colloquium on the Similarity and Diversity of Comets, ESA SP-278 (in press)
5. Cercignani, C.: 1981, Progr. Astron. Aeron. 74, Vol. 1, p. 305