1. Association of American Feed Control Officials, 1973. Page 62 in: Official Publication. Association of American Feed Control Officials, Charleston, WV.
2. Methods Used and Adopted,1991
3. Methods of Analysis,1984
4. Minerals in Animal and Human Nutrition;McDowell,1992
5. National Research Council, 1980. Mineral Tolerance of Domestic Animals. National Academy Press, Washington, DC.