1. Geerligs, L.J., Anderegg, V.F., Holweg, P.A.M., Mooij, J.E., Pothier, H., Est�ve, D., Urbina, C., Devoret, M.H.: Phys. Rev. Lett.64, 2691 (1990)
2. Pothier, H., Lafarge, P., Orfila, P.F., Urbina, C., Est�ve, D., Devoret, M.H.: Physica B169, 573 (1991)
3. See, e.g., the review papers in: Grabert, H., Devoret M.H. (eds.): Proceedings of the NATO ASI onSingle Charge Tunneling, Les Houches, March 1991. New York: Plenum Press 1992; Averin, D.V., Likharev, K.K.: In: Mesoscopic phenomena in solids. Altshuler, B.L., Lee, P.A., Webb, R.A. (eds.). Chap. 6, p. 167. Amsterdam: Elsevier 1991
4. Fulton, T.A., Dolan, G.J.: Phys. Rev. Lett.59, 109 (1987)
5. This threshold voltage, characteristic for Coulomb blockade effects, is inversely proportional to the junction capacitance. See, e.g., D. Est�ve, in Ref. 3,, or Ref. 10 Geerligs, L.J.: Classical and quantum charge dynamics in small tunnel junctions. Thesis, Delft University of Technology (1990)