1. Bray, G. A.: Analyt. Biochem.1, 279 (1960).
2. Grimmett, M., Richards, E. L.: Aust. J. Chem.18, 1855 (1965).
3. Ibanez, J. D., Kimball, A. P., Oro, J.: Science (in press).
4. —, —, —, In Chemical evolution and the origin of life (edit. by Buvet, R., and Ponnamperuma, C.). Amsterdam: North-Holland 1971.
5. Ibanez, J., Oró, J., Kimball, A. P.: Abstracts, Amer. Chem. Soc. Southwest Regional Meeting. Tulsa, Oklahoma, December 1969.