1. S. G. Rautian, Usp. Fiz. Nauk,66, 475 (1958).
2. V. F. Turchin, V. P. Kozlov, and M. S. Malkevich, Usp. Fiz. Nauk,102, 345 (1970).
3. N. G. Preobrazhenskii and B. Z. Tambovtsev, Opt. Spektrosk.,35, 946 (1973).
4. A. N. Tikhonov and V. Ya. Arsenin, Methods for the Solution of Improper Problems [in Russian], Nauka, Moscow (1974).
5. V. S. Babaev and V. V. Kuchinskii, Opt. Spektrosk.,45, 374 (1978).