1. D.V. Averin and K.K. Likharev, in Mesoscopic Phenomena in Solids, ed. B.L. Altshuler, P.A. Lee and R.A. Webb (Elsevier, Amsterdam, 1991), p. 173
2. Several review articles are contained in Single Charge Tunneling, NATO ASI Series, Vol. 294, H. Grabert and M.H. Devoret, eds., New York, Plenum Press (1992)
3. For further articles we refer to Z.Phys.B-Condensed Matter 85 (1991)
4. I.O. Kulik and R.I. Schekhter, Sov. Phys. JETP 41, 308 (1975)
5. G. Schön and A.D. Zaikin, Phys. Rep. 198, 237 (1990)