Lawrie, A. H. 1970. The sea lamprey in the Great Lakes. Transactions of the American Fisheries Society 99:766-775. Leach, J. H., M. G. Johnson, J. R. M. Kelso, J. Hartmann, W. Numann, and B. Entz. 1977. Responses of percid fishes and their habitats to eutrophication. Journal of Fisheries Research Board of Canada 34:1964-1971. Lelek, A. 1987. The freshwater fishes of Europe: Threatened fishes of Europe. Volume 9. AULA-Verlag, Wiesbaden.