1. Averin, D.V., Likharev, K.K.: In: Mesoscopic Phenomena in Solids (to appear). Altshuler, B.L., Lee, P.A., Webb, R.A. (eds.). Amsterdam: Elsevier 1991
2. Sch�n, G., Zaikin, A.D.: Phys. Rep.198, 237 (1990)
3. For a review see e.g.: Grabert, H., Devoret, M.H. (eds.): Proceedings of the NATO ASI onSingle Charge Tunneling, Les Houches 1991, New York: Plenum Press 1992
4. Geerligs, L.J., Anderegg, V.F., Holweg, P., Mooij, J.E., Pothier, H., Esteve, D., Urbina, C., Devoret, M.H.: Phys. Rev. Lett.64, 2691 (1990)
5. Pothier, H., Lafarge, P., Orfila, P.F., Urbina, C., Esteve, D., Devoret, M.H.: Physica B169, 573 (1991)