  It is shown that the steady unidirectional flow with vanishing heat flux
considered by B. C. Eu [Phys. Rev. E 65, 031202 (2002)], and earlier by Uribe
and Garcia--Colin [Phys. Rev. E 60, 4052 (1999)], is inconsistent with the
exact conservation laws of mass, momentum, and energy. The inconsistency does
not lie in the assumed symmetry properties of the flow but in the stationarity
assumption. The unsteady problem is considered and its solution from the
Boltzmann equation for Maxwell molecules is given.
