[1] T.A. Witten and L.M. Sander, Phys. Rev. Lett, 47, 1400
(1981).
[2] P. Meakin, in Phase Transitions and Critical Phenomena,
eds. C. Domb and J. L. Lebowitz, Vol.12 (Academic, NY,
1988).
[3] M. B. Hastings and L. S. Levitov, Physica D 116, 244
(1998).
[4] B. Davidovitch, H. G. E. Hentschel, Z. Olami, I. Procaccia,
L. M. Sander, and E. Somfai, Phys. Rev. E 59, 1368
(1999).
[5] T. A. Witten and L. M. Sander, Phys. Rev. B 27, 2586
(1983).
[6] L. Niemeyer, L. Pietronero and H.J. Wiessmann, Phys.
Rev. Lett. 52, 1033 (1984).
[7] M. Plischke and Z. R´acz, Phys. Rev. Lett. 53, 415 (1984)
[8] P. Meakin and L. M. Sander, Phys. Rev. Lett. 54, 2053
(1985).
[9] B. B. Mandelbrot, H. Kaufman, A. Vespignani, I. Yekutieli,
and C.-H. Lam, Europhys. Lett. 29, 599 (1995).
[10] W. W. Mullins and R. F. Sekerka, J. Appl. Phys. 34, 323
(1963).
[11] T.C. Halsey, P. Meakin and I. Procaccia, Phys. Rev. Lett.
56, 854 (1986).
[12] This estimate differs from the calculation in Appendix B
of Ref. [4] because in that paper |Z| in our Eq.6 was
implicitly replaced by ro. We believe this to be too crude
an approximation.
[13] P. W. Barker and R. C. Ball, Phys. Rev. A 42,6289
(1990).
[14] R. C. Ball, L. M. Sander, and E. Somfai, to be published.