1. V.V. Dodonov, I.A. Malkin, V.I. Manko, Physica 72, 597 (1974)
2. C.C. Gerry, Opt. Commun. 91, 247 (1992)
3. V. Buzek, A. Vidiella-Barranco, P.L. Knight, Phys. Rev. A 45, 6750 (1992)
4. C.C. Gerry, J. Mod. Opt. 40, 1053 (1993)
5. V. Buzek, P.L. Knight, in Progress in optics, edited by E. Wolf (North Holland, Amsterdam, 1995), Vol. XXXIV