  In this paper we investigate arithmetic properties of automorphic forms on
the group G' = GL_m/D, for a central division-algebra D over an arbitrary
number field F. The results of this article are generalizations of results in
the split case, i.e., D=F, by Shimura, Harder, Waldspurger and Clozel for
square-integrable automorphic forms and also by Franke and Franke-Schwermer for
general automorphic representations. We also compare our theorems on
automorphic forms of the group G' to statements on automorphic forms of its
split form using the global Jacquet-Langlands correspondence developed by
Badulescu and Badulescu-Renard. Beside that we prove that the local version of
the Jacquet-Langlands transfer at an archimedean place preserves the property
of being cohomological.
