1. Rafter, T. A., NZ J. Sci., 10, 493 (1967).
2. Rafter, T. A., and Mizutani, Y., NZ J. Sci., 10, 816 (1967).
3. Rafter, T. A., NZ J. Sci. Tech. B., 38, 849 (1957).
4. Longinelli, A., and Craig, H., Science, 156, 56 (1967).
5. Teis, R. V., Geokhimiya, 3, 257 (1956).