1. D. Adler and M. Mathur, 1973, private communications.
2. D. Buckley, 1973, private communication.
3. Y. Chang and S.R. Ovshinsky, 1973, unpublished.
4. M.H. Cohen, H. Fritzsche and S.R. Ovshinsky, 1969, Phys. Rev. Lett. 22, 1065.
5. J. deNeufville, S.C. Moss and S.R. Ovshinsky, 1973, Proceedings of the Fifth International Conference on Amorphous and Liquid Semiconductors, Garmisch-Partenkirchen.