  In a recent publication, J. Phys.: Condens. Matt. 14 13777 (2002), Kuzovkov
et. al. announced an analytical solution of the two-dimensional Anderson
localisation problem via the calculation of a generalised Lyapunov exponent
using signal theory. Surprisingly, for certain energies and small disorder
strength they observed delocalised states. We study the transmission properties
of the same model using well-known transfer matrix methods. Our results
disagree with the findings obtained using signal theory. We point to the
possible origin of this discrepancy and comment on the general strategy to use
a generalised Lyapunov exponent for studying Anderson localisation.
