1. Streeton, R. J. W., Atomic Energy Res. Est. Mem., C/M, 168 (1953).
2. Sverdrup, H. V., Johnson, M. W., and Fleming, R. H., The Oceans (Prentice-Hall Inc., New York, 1946).
3. Koczy, F. F., Nuclear Geology (Chapman and Hall, London, 1954).
4. Wilson, J. D., Webster, R. K., Milner, G. W. C., Barnett, G. A., and Smales, A. A., Anal. Chim. Acta., 23, 505 (1960).
5. Kennedy, J. (unpublished work).