1. See for example D.J. Wineland, W.M. Itano, and R.S. Van Dyck, Jr.: Adv. At. Mol. Phys. 19, 135 (1983) and references therein
2. F.L. Walls: Proc. of the IEEE 74, 142 (1986)
3. D.J. Wineland, W.M. Itano, J.C. Bergquist, and F.L. Walls: in Proc. of 35th Ann. Freq. Control Symposium (USAERADCOM, Ft. Monmouth, NJ 07703) p. 602 (1981)
4. D.J. Wineland, in Precision Measurement and Fundamental Constants II, ed. by B.N. Taylor and W.D. Phillips (Natl. Bur. Stands. (U.S) Spec. Publ. 617, 1984), p. 83
5. J.J. Bollinger, J.D. Prestage, W.M Itano, and D.J. Wineland: Phys. Rev. Lett. 54, 1000 (1985)