1. American Public Health Association, American Water Works Association, and Water Pollution Control Federation, 1975: Standard Methods for the Examination of Water and Wastewater. 14th ed. Washington, D.C.: American Public Health Association Publication Office. 1139 pp.
2. Birkeland, P. W., 1999: Soils and Geomorphology. 3rd ed. New York: Oxford University Press. 430 pp.