1. Symposium on Tektites, Geochim. Cosmochim. Acta, 14 (1958).
2. Hawkins, G. S., Nature, 185, 300 (1960).
3. Shapiro, L., and Brannock, W., U.S. Geol. Survey Bull., 1036-C (1956).
4. Senftle, F. E., and Thorpe, A., Geochim. Cosmochim. Acta, 17, 234 (1959).
5. Abou-el-azm, A., Trans. Soc. Glass Tech., 38, 101 (1954).