1. North American tektites;Barnes;Univ. Tex. Publ. No. 3945,1940
2. Cassidy W. (1957) Personal communication.
3. Silica-glass from the Libyan Desert;Clayton;Miner. Mag.,1934
4. Friedman I. (1957) Personal communication (See his article in this issue).
5. Infrared and Raman Spectra;Herzberg,1945