1. A. Yariv: Quantum Electronics, 2nd edn. ( Wiley and Sons, New york 1975 ), Chap. 6
2. J.A. Arnaud: Beam and Fiber Optics (Academic Press, New York 1976), Chaps. 2, 4
3. D. Marcuse: Light Transmission Optics, 2nd edn. ( Van Nostrand Reinhold, New York 1982 ), Chap. 7
4. A.E. Siegman: Lasers (University Science, Mill Valley 1986), Chap. 20
5. N. Hodgson, H. Weber: Optical Resonators: Fundamentals, Advanced Concepts and Applications (Springer-Verlag, Berlin 1997 ), Part IV