1. V. S. Letokhov, Usp. Fiz. Nauk,118, No. 2, 199?249 (1976).
2. W. Walter (ed.). Laser Spectroscopy of Atoms and Molecules [Russian translation], Mir, Moscow (1979), pp. 28?40.
3. V. S. Letokhov, Usp. Fiz. Nauk,125, No. 1, 57?96 (1978).
4. A. Z. Grasok, V. S. Letokhov, and V. V. Lobko, Kvantovaya Elektron.,7, No. 11, 2261?2298 (1980).
5. Preprints No. 2;S. F. Dyubko,1979