1. D. E. Onopko, N. T. Bagraev, and A. I. Ryskin,Fiz. Tverd. Tela,37, No. 8, 2376–2397 (1995).
2. D. E. Onopko and A. I. Ryskin,Opt. Spektrosk.,84, No. 1, 56–64 (1998).
3. I. B. Bersuker and V. Z. Polinger,Vibronic Interactions in Molecules and Crystals [in Russian], Nauka, Moscov (1983).
4. A. Zunger,Solid State Phys.,39, 275–464 (1986).
5. G. D. Watkins,Rev. Solid State Sci.,4, 279–295 (1990).