1. D.T. Peterson, Environmental Law Information Resources Home Page. http://www.envinfo.com, accessed May 2003.
2. M.J. Udy, Chromium: Chemistry of Chromium and its Compounds, vol. 1, Reinhold Publishing Corporation, New York; Chapman & Hall Ltd., London, 1956.
3. Direct and Simultaneous Determination of Copper, Chromium, Aluminum, and Manganese in Urine with a Multielement Graphite Furnace Atomic Absorption Spectrometer
4. U.S. Environmental Protection Agency Home Page. http://www.epa.gov, accessed November 2002.