Comment on: "Roughness of Interfacial Crack Fronts: Stress-Weighted   Percolation in the Damage Zone"
  This is a comment on J. Schmittbuhl, A. Hansen, and G. G. Batrouni, Phys. Rev. Lett. 90, 045505 (2003). They offer a reply, in turn. 
M.J. Alava and S. Zapperi