1. Craig, J.F. (1980) Growth and production of the 1955–1972 cohorts of perch, Perca fluviatilis L. in Windermere. Journal of Animal Ecology 49, 291–315.
2. Elton, C. (1942) Voles, mice and lemmings: problems in population dynamics. Oxford University Press, London.
3. Hellawell, J.M. (1977) Change in natural and managed ecosystems: detection, measurement and assessment. Proceedings of the Royal Society. London B: 197, 31–57.
4. Hellawell, J.M. (1978) Biological surveillance of rivers. Medmenham and Stevenage: Water Research Centre.
5. Hellawell, J.M. (1986) Biological indicators of freshwater pollution and environmental management. Elsevier Applied Science Publisher, London.