  The standard ohmic measurements by means of two extra leads contain an
additional thermal correction to resistance. The current results in
heating(cooling) at first(second) sample contact due to Peltier effect. The
contacts temperatures are different. The measured voltage is the sum of the
ohmic voltage swing and Peltier effect induced thermopower which is linear on
current. As a result, the thermal correction to resistance measured exists at
$I\to 0$. The correction should be in comparison with ohmic resistance. Above
some critical frequency dependent on thermal inertial effects the thermal
correction disappears.
