1. Fowler, G. J., "An Introduction to the Biochemistry of Nitrogen Conservation" (London, 1934), p. 247.
2. Mathews, A. P., "Physiological Chemistry" (New York, 1924). 3rd Edit., p. 755.
3. Quoted by Lester, J. S., "Nutrition and Diet in Health and Disease" (London, 1934), 2nd Edit., p. 121.
4. Armstrong, E. F., NATURE, 150, 453 (1942).