\bibitem{Sapoval93}     B.Sapoval, R.Gutfraind, P.Meakin, M.Keddam, H.Takenouti    \hskip 2mm
                        {\it Equivalent-Circuit, Scaling, Random-Walk Simulation, and an Experimental Study of 
                        Self-Similar Fractal Electrodes and Interfaces},
                        Phys.Rev. E {\bf 48}, 3333-3344, 1993.