1. Dendy, J. S., Ecol. Mon., 14, 333 (1944).
2. Wolff, Ph., Skrifter fran Svenska Lax-och Laxöringsförening, 1 (Gleerup, Lund, Sweden, 1947).
3. Müller, K., Rep. Inst. Freshwater Res. Drottningholm, 35, 133 (1953).
4. Waters, T. F., Ecology, 42, 532 (1961).
5. Müller, K., Naturwiss., 5, 161 (1963).