  Recently, Tieke et al (to be published in PRL) have observed the relation
S_{yx} = alpha B dS_{xx}/dB for the components of the thermopower tensor in the
quantum Hall regime, where alpha is a constant and B is the magnetic field.
Simon and Halperin (PRL 73, 3278 (1994)) have suggested that an analogous
relation observed for the resistivity tensor R_{xx} = \alpha B dR_{xy}/dB can
be explained with a model of classical transport in an inhomogeneous medium
where the local Hall resistivity is a function of position and the local
dissipative resistivity is a small constant. In the present paper, we show that
this new thermopower relation can be explained with a similar model.
