1. Alabaster, J. S. and Lloyd, R. 1980.Water quality criteria for freshwater fish, 297Butterworths: United Nations Food and Agriculture Organisation.
2. APHA. 1985.Standard methods for the examination of water and wastewater, (16th edition), 1133American Public Health Association, American Water Works Association and Water Pollution Control Federation.
3. Water and soil miscellaneous publication 47;Biggs B. J. F.,1982
4. Periphyton biomass dynamics in gravel bed rivers: the relative effects of flows and nutrients