1. Yu. A. Anan'ev, Optical Resonators and the Problem of the Divergence of Laser Radiation [in Russian], Nauka, Moscow (1979).
2. H. Bateman and A. Erdelyi, High Transcendental Functions [Russian translation], Nauka, Moscow (1974).
3. J. Boyd and J. Gordon, ?Confocal resonator with many types of oscillations for millimeter and optical lasers,? in: Lasers [Russian translation] IL, Moscow (1963), pp. 363?383.
4. M. Born and E. Wolf, Principles of Optics, Pergamon Press, New York (1959).
5. Ya. S. Bugrov and S. M. Nikol'skii, Elements of Linear Algebra and Analytic Geometry [in Russian], Nauka, Moscow (1980).