1. P. F. Moulton, Laser Focus, p. 83, May 1983.
2. P. F. Moulton, CLEO Tech. Digest, WA2, p. 77, June 1984.
3. G. F. Albrecht, J. M. Eggleston and J. J. Ewing, 1st Annual Conference on Tunable Solid State Lasers, June 1984, La Jolla Inst., La Jolla, CA.