Caract\`eres automorphes d'un groupe r\'eductif
  Let $G$ be a reductive group defined over a number field. Denote $Z(\hat G)$ the center of the dual group. Langlands has defined some homomorphism from some cohomology group of $Z(\hat G)$ into the group of automorphic characters of $G$. We prove that it is bijective. 
J.-L Waldspurger (IMJ-PRG)
math.RT