1. Callendar, G. S., Tellus, 10, 243 (1958).
2. Machta, L., in Carbon and the Biosphere, Brookhaven Symp. Biol., No. 24 (edit. by Woodwell, G. M., and Pecan, E. V.) (USAEC. Washington, DC., in the press).
3. Baxter, M. S., and Walton, A., Proc. R. Soc., A318, 213 (1970).
4. Broecker, W. S., Li, Y. H., and Peng, T. H., in Impingement of Man on the Oceans (edit. by Hood, D. W.), 287 (Wiley, New York, 1971).
5. Craig, H., Geochim. cosmochim. Acta, 3, 53 (1953).