1. B. L Schumaker, Opt Letters, 9, 89, (1984).
2. A. E. Siegman, Lasers. (Science Books, Mill Valley, California, 1986) Chapters 14–17.
3. Ibid, Chapter 11.
4. M.D. Levenson, W.H. Richardson, S.H. Perlmutter, Opt. Letters, (submitted).
5. D.H. Auston, IEEE J. Quantum Electron., QE-4, 420, (1968)