1. The oldest rocks exposed;Ahrens;Geol. Soc. Amer., Special paper,1955
2. Chemical evolution and the origins of life;Calvin;Am. Scientist,1956
3. The origin of life;Haldane;Rationalist Annual,1929
4. Darwin and the heterotroph hypothesis;Hardin;Sci. Monthly,1950
5. The oldest dated minerals of the Rhodesian shield;Holmes;Nature,1950