1. Fell, H. B., Phil. Trans. Roy. Soc., B, 246, 381 (1963).
2. Philip, G. M., Nature, 208, 766 (1965).
3. Fell, H. B., Nature, 208, 768 (1965).
4. Bergmann, W., in Comparative Biochemistry (edit. by Florkin, M., and Mason, H. S.), 3, A, chapter 2 (Academic Press, New York, 1962).
5. Bolker, H. I. dissert. Yale Univ. (1952).