1. C. W. Turner: Univers. of Missouri, College of Agricult. Exp. Stat. Bull. 346; Milchw. Forsch., Ref. 1935, 17, 143.
2. B. Houcrin, W. R. Graham, V. E. Peterson, C. W. Turner: Journ. Dairy Sci. 1939, 22, 241; Milchw. Forsch., Ref. 1940, 20, 257.
3. D. Michlin, M. Levitow, T. Fetissowa: Biochem. Zeitschr. 1934, 271, 448; 1935, 282, 26.
4. Ph. L. Kelly, W. C. E. Petersen: Journ. Dairy Sci. 1939, 22, 7.
5. V. N. Nikitin: Milchw. Forsch., Ref. 1936, 18, 2.