1) A. O. A. C., Official Methods of Analysis of the Association of Official Agricultural Chemists,Publ. Association of Official Agricultural Chemists, Washington, D. C. (1965).
2) L. R. WETTER, Can. J. Biochem. Physiol., 33, 980 (1955).
3) S. KINOSHITA, In Biochemistry of Industrial Microorganisms, ed. by C. RAINBOW and A. H. ROSE, Academic Press, London (1963), p. 206.