1. Howell, F. C., Nature, 219, 567 (1968).
2. Arambourg, C., and Coppens, Y., CR Acad. Sci. Paris, 265, 589 (1967).
3. Arambourg, C., and Coppens, Y., S. Afr. J. Sci., 64, 58 (1968).
4. Patterson, B., and Howells, W. W., Science, 156, 64 (1967).
5. Martyn, J., and Tobias, P. V., Nature, 215, 476 (1967).