  We emphasize the importance of the position dependence of the diffusion
coefficient D(r) in the self-consistent theory of localization and argue that
the scaling law T ~ ln(L)/L^2 obtained by Cheung and Zhang [Phys. Rev. B 72,
235102 (2005)] for the average transmission coefficient T of a disordered slab
of thickness L at the localization transition is an artifact of replacing D(r)
by its harmonic mean. The correct scaling T ~ 1/L^2 is obtained by properly
treating the position dependence of D(r).
