1. Wineland, D.J.: Science226, 395 (1984
2. Thompson, R.C., Barwood, G.P., Gill, P.: Appl. Phys. B46, 87 (1988)
3. Bollinger, J.J., Prestage, J.D., Itano, W.M., Wineland, D.J.: Phys. Rev. Lett.54, 1000 (1985)
4. Cutler, L.S., Giffard, R.P., Wheeler, P.J., Winkler, G.: Proceedings of the Frequency Control Symposium, Philadelphia 1987
5. Strumia, F.: Proceedings of the 32nd. Annual Symposium on Frequency Control, Atlantic City, N.J., USA 1978