1. Z. Burshtein, Y. Shimony, R. Feldman, V. Krupkin, A. Glushko, E. Galun, Opt. Mater. 15 (2001) 285.
2. M. Birnbaum, M. B. Camargo, S. Lee, F. Unlu, R.D. Stultz, OSA TOPS 10 Adv. Solid State Lasers 148 (1997) 132.
3. S. Golab, Z. Mierczyk, W. Ryba-Romanowski, Phys. Stat. Sol. (a) 179 (2000) 463.
4. R.D. Stultz, M.B. Camargo, M. Birnbaum, OSA Proc. Adv. Solid-State Lasers 24 (1995) 460.
5. Hi Song, Singapore Scientific Corp. Ed., 1993, p. 132