1. Miyazawa, H., Maeda, H., Tomishima, H.: J. Phys. Soc. Jpn. 14 (1959) 41.
2. Piper, W. W., Halsted, R. E.: Proc. 5th Int. Conf. Phys. Semicond., Prague, Academic Press, New York/London, 1961, 1046.
3. Holland, M. G.: Phys. Rev. 134 (1964) A 471.
4. Woodbury, H. H.: Proc. 7th Int. Conf. II-VI Semiconducting Compounds, Providence, R. T., USA, W. A. Benjamin Inc., New York, 1967, 244.
5. Crandall, R. S.: Phys. Rev. 169 (1968) 577.