Abstract. 
In this informal talk I will review a paper written by Eckmann et al. The
model is a chain of anharmonic oscillators coupled to two heat baths
described by wave equations. Under some assumption, one can prove that (1)
there exists an invariant measure and (2) the invariant measure is unique
when the temperature difference is sufficiently small. The techniques are
based on an extension of the commutator method of Hormander.