1. H. J. Queisser in: Festkörperprobleme XI—Advances in Solid State Physics, Pergamon-Vieweg (1971), p. 45.
2. see: A. G. Milnes, Deep Impurities in Semiconductors, New York, Wiley (1973) and references therein.
3. G. L. Miller, D. V. Lang and L. C. Kimerling, Ann. Rev. Mater. Sci. (1977), p. 377.
4. H. G. Grimmeiss, Ann. Rev. Mater. Sci. (1977), p. 341.
5. A. Micea and D. Bois, Inst. Phys. Conf. Ser. 46, p. 82 (1979).