AOAC International (1997a) Official Methods of Analysis, 16th ed., 3rd rev. (ed. by Cunniff, P.), AOAC International, Gaithersburg, MD, USA, 39.1.19 (981.10)
AOAC International (1997b) Official Methods of Analysis, 16th ed., 3rd rev. (ed. by Cunniff, P.), AOAC International, Gaithersburg, MD, USA, 44.1.05 (900.02 C)