1. Kark, E., 1953. S. Afr. J. med. Sci. 18, 190.
2. Wintrobe, M. M., 1946. Clinical Haematology. Lea and Febiger, Philadelphia.
3. Lipmann, F., 1956. Currents in Biochemical Research. Interscience, London.
4. Spiegelman, S., Halvorson, H. O. and Ben-Ishai, 1955. In: Amino Acid Metabolism. Johns Hopkins Press, Baltimore.
5. Zamecrick, P. C. and Keller, E. B., 1954. J. biol. Chem. 209, 337.