Formal structure of direct image of holonomic D-modules of exponential   type
  We compute formal invariants associated with the cohomology sheaves of the direct image of holonomic D-modules of exponential type. We also prove that every formal C[[t]]<\partial_t>-modules is isomorphic, after a ramification, to a germ of formalized direct image of analytic D-module of exponential type. 
C. Roucairol