1. Allen, S.W., Fabian, A.C., Johnstone, R.M., Nulsen, P.E.J. & Edge, A.C., 1991. Mon. Not. R. astr. Soc. in press.
2. Amaud, K.A., 1988. In Cooling Flows in Clusters and Galaxies, ed. A.C. Fabian, Kluwer, 31.
3. Amaud, K.A. et al., 1991. In Proc. 28th Yamada Conference, eds. K. Koyama & Y. Tanaka, in press.
4. Bahcall, N.A. & Choksi, A., 1991. Astrophys. J., 380, L9.
5. Balbus, S., 1988. Astrophys. J., 328, 395.