  The derivation of the Navier-Stokes equation starting from the Liouville
equation using projector techniques yields a friction term which is nonlinear
in the velocity. As has been explained in the 1. version of this paper, when
the second-order part of the term is non-zero, this leads to an incorrect
formula for the equation.
  In this 2. version, it is shown that the problem is due to an inadequate
treatment of one of the correlation functions appearing . Repeating the
calculation leads to zero second-order part. The Navier-Stokes equation is
correctly derived by projection operator technique.
