1. Moulton P.F.: Conference on Lasers and Electro-Optics, Annaheim, Ca., (USA) 1982.
2. Budgor A.B., Esterowitz L., De Shazer L.G. (editors): Tunable Solid State Lasers II. Springer Verlag, Berlin-New York-London, 1986, p. 202.
3. Kaminskii A.A.: Fizika i spektroskopiya lasernykh kristallov, Nauka, Moscow, 1986, p. 44.
4. Schepler K.L.:in Tunable Solid State Lasers II. (see ref. /1/), p. 235.
5. Kokta M.R.: Laser and Nonlinear Optical Materials, SPIE681 (1981) p. 50.