1. Groom, M. & Schumaker, N. in Biotic Interactions and Global change (eds Kareiva, P., Kingsolver, J. & Huey, R.) 24–44 (Sinauer, Sunderland, 1993).
2. Noss, R. & Csuti, B. in Principles of Conservation Biology (eds Meffe, G. & Carroll, C.) 237–264 (Sinauer, Sunderland, 1994).
3. Hastings, A. & Higgins, K. Science 263, 1133–1136 (1994).
4. Tilman, D., May, R., Lehman, C. & Nowak, M. Nature 371, 65–66 (1994).
5. Sabelis, M. & Diekmann, O. Theor. Pop. Biol. 34, 169–176 (1988).