1. AOAC. (1990a).Official Methods of Analysis of the Association of Official Analytical Chemists.Volume I, Section 942.05. 15th Edition, Association of Official Analytical Chemists, Arlington, VA, USA. 853 pp.
2. AOAC. (1990b).Official Methods of Analysis of the Association of Official Analytical Chemists.First Supplement. Section 990.03. 15th Edition. Association of Official Analytical Chemists, Arlington, VA, USA. 910 pp.
3. AOAC. (1990c).Official Methods of Analysis of the Association of Official Analytical Chemists.(Helrich, K. Ed.). Association of Official Analytical Chemists, Arlington, VA, USA. 801 pp.