INVARIANT FUNDAMENTAL-SOLUTIONS FOR INVARIANT DIFFERENTIAL-OPERATORS ON REDUCTIVE SYMMETRICAL SPACES OF TYPE G(C) G(R)/

Let G be a complex connected reductive group with simply connected der ived group. Let H be a real form of G. Let z be a G-invariant differen tial operator on the reductive symmetric space G/H. We give an explici t sufficient condition for z to have an invariant fundamental solution on G/H. (C) Academie des Sciences/Elsevier, Paris.