1. S. G. Rautian, G. I. Smirnov, and A. M. Shalagin, Non-linear Resonances in Atomic and Molecular Spectra (Nauka, Novosibirsk, 1979).
2. A. K. Popov, Introduction to the Nonlinear Spectroscopy (Nauka, Novosibirsk, 1983); Izv. Akad. Nauk, Ser. Fiz. 60, 99 (1996).
3. S. E. Harris, Phys. Today 50(7), 36 (1997).
4. S. E. Harris and Y. Yamamoto, Phys. Rev. Lett. 81, 3611 (1998).
5. S. E. Harris and V. H. Lene, Phys. Rev. Lett. 82, 4611 (1999).