1. V. S. Letokhov and V. P. Chebotaev, Nonlinear Laser Ultrahigh-Resolution Spectroscopy (Nauka, Moscow, 1990) [in Russian].
2. S. G. Rautian, G. I. Smirnov, and A. M. Shalagin, Nonlinear Resonances in Spectra of Atoms and Molecules (Nauka, Novosibirsk, 1979) [in Russian].
3. A. K. Popov, Introduction to Nonlinear Spectroscopy (Nauka, Novosibirsk, 1983) [in Russian].
4. W. Demtröder, Laser Spectroscopy: Basic Concepts and Instrumentation (Springer-Verlag, Berlin, 1980; Nauka, Moscow, 1985)].
5. S. Stenholm, Foundations of Laser Spectroscopy (Wiley, New York, 1984; Mir, Moscow, 1987).