\bibitem{Pfeifer84}     P.~Pfeifer, D.~Avnir, D.~Farin,
                        {\it Scaling Behavior of Surface Irregularity in the Molecular Domain: From Adsorption Studies to Fractal Catalysis},
                        J. Stat. Phys. {\bf 36} (5/6), 699, 1984.