1. Bi-symmetric instabilities of the Kuz'min/Toomre disc
2. A hierarchical O(N log N) force-calculation algorithm
3. Binney, J. & Tremaine, S. 1987, Galactic Dynamics (Princeton: Princeton Univ. Press)
4. Bodenheimer, P., Ruzmaikina, T. & Mathiew, R. D. 1993, in Protostars and Planets III, ed. E. H. Levy & J. I. Lunine (Tucson: Univ. of Arizona Press), 367