  Fendley, Ludwig and Saleur [Phys. Rev. B52 (1995) 8934] have obtained an
expression for the non-equilibrium current through a constriction in the
quantum Hall bar based on the Bethe ansatz technique and the Bolzmann equation.
In this Comment we draw attention to a serious flaw in their derivation. We
argue that their result is correct in the linear response limit but should be
taken with a care out of equilibrium for finite bias. The reason is in the use
of the equilibrium scattering matrix in the place of the transition probability
amplitude out of equilibrium, the substitution which was not shown to be
legimate.
