1. L. S. Vasilenko, V. P. Chebotaev, and A. V. Shishaev, JETP Lett. 12, 113 (1970).
2. V. S. Letokhov and V. P. Chebotaev, Nonlinear Laser Superhigh Resolution Spectroscopy (Nauka, Moscow, 1990) [in Russian].
3. E. V. Baklanov and V. P. Chebotayev, Opt. Commun. 12, 312 (1974).
4. E. V. Baklanov and V. P. Chebotaev, Opt. Spectrosc. 38, 215 (1975).
5. M. Niering, R. Holzwarth, J. Reichert, P. Pokasov, Th. Udem, M. Weitz, T. W. Hansch, P. Lemonde, G. Santarelli, M. Abgrall, P. Laurent, C. Salomon, and A. Clairon, Phys. Rev. Lett. 84, 5496 (2000).