1. I. N. Ogorodnikov, A. V. Kruzhalov, and V. A. Maslov, Zh. Prikl. Spektrosk.,49, No. 1, 134?136 (1988).
2. K. N. Giniyatulin, A. V. Kruzhalov, and B. V. Shul'gin, Radiation-Stimulated Phenomena in Solids: Intercollegiate Coll. [in Russian], Sverdlovsk (1982), pp. 3?12.
3. R. A. Évarestov, E. A. Kotomin, and A. N. Ermoshkin, Molecular Models for Point Defects in Wide-Gap Solids [in Russian], Riga (1983).
4. A. N. Vasil'ev, K. B. Topornin, and R. A. Évarestov, Opt. Spektrosk.,48, No. 2, 277?282 (1982).
5. L. M. Brescansin and L. G. Ferreira, Phys. Rev. B,20, No. 8, 3415?3421 (1979).