1. Wilson, P. W., “The Biochemistry of Symbiotic Nitrogen Fixation”, 302 (Univ. of Wisconsin Press, Madison, 1940). Burk, D., and Burris, R. H., “Ann. Rev. Biochem.”, 10, 587 (1941). Burris, R. H., and Wilson, P. W., ibid., 14, 685 (1945).
2. Steinberg, R. A., J. Agric. Res., 52, 439 (1936); 55, 891 (1937).
3. Oparin, A. I., “The Origin of Life” (Macmillan, New York, 1938).
4. Urey, H. C., Proc. U.S. Nat. Acad. Sci., 38, 351 (1952); “The Planets”, Chapter 4 (Yale Univ. Press, New Haven, 1952).
5. Bernal, J. D., Proc. Phys. Soc. Lond., A, 62, 537 (1949); B, 62, 597 (1949); “Physical Basis of Life” (Routledge and Kegan Paul, London, 1951).