1. Ch. B. Lushchik, Tr. Inst. Fiz. Astron. Akad. Nauk Est., No. 3, 230 (1995).
2. G. Chiarott and N. Inchauspe, Phys. Rev. 109(2), 345 (1958).
3. R. G. Kaufman and W. B. Hadley, J. Chem. Phys. 47(1), 264 (1967).
4. É. D. Aluker, D. Yu. Lusis, and S. A. Chernov, Electronic Excitations and Radioluminescence in Alkali Halide Metals (Zinatne, Riga, 1979) [in Russian].
5. H. von Seggern, Cryst. Lattice Defects Amorphous Mater. 18(1–3), 399 (1989).