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2. M.H. Cohen, J. Singh and F. Yonezawa: J. Non-Cryst. Solids 36 55 (1980)
3. M.H. Cohen, H. Fritzsche, J. Singh and F. Yonezawa: to be published in Proc. 15th Int. Conf. on the Physics of Semiconductors, Kyoto, Sept. 1–5 (1980)
4. M.H. Cohen, J. Singh and F. Yonezawa: Solid State Communications (in press)
5. J. Singh and M.H. Cohen: submitted to Phys. Rev. Letters