1. Knoop, F., Beitr. Chem. Physiol. Pathol. 6:150 (1905).
2. Schoenheimer, R., “The Dynamic State of Body Constitutents,” Harvard University Press, Cambridge, 1942.
3. Calvin, M., “Isotopic Carbon” John Wiley & Sons, Inc., New York, 1949.
4. Rynhagen, R., Anal Chem. 36:759 (1964).
5. Rynhagen, R., S. Wikstron, and G. R. Woller, Ibid. 37:435 (1965).