1. J. Steininger, Paper presented at ACCG III, Stanford University (1975), to be published in J. Crystal Growth.
2. R. F. Brebrick and A. J. Strauss, J. Phys. Chem. Solids26, 989 (1965).
3. B. Ray and P. M. Spencer, Phys. Status Solidi22, 371 (1967).
4. J. Blair and R. Newnham, Metallurgy of Elemental and Compound Semiconductors, (Interscience Publishers, Inc., New York, 1961), Vol. 12.
5. T. C. Harman, Physics and Chemistry of II-VI Compounds (Interscience Publishers, Inc., New York, 1967).