\bibitem{Hentschel02}   H.G.E.~Hentschel, A.~Levermann, I.~Procaccia,
                        {\it Transition in the Fractal Properties from Diffusion-Limited Aggregation to
                        Laplacian Growth via Their Generalization},
                        Phys.~Rev. E {\bf 66}, 016308, 2002.