Parametrices and hypoellipticity for pseudodifferential operators on   spaces of tempered ultraditributions
  We construct parametrices for a class of pseudodifferential operators of infinite order acting on spaces of tempered ultradistributions of Beurling and Roumieu type. As a consequence we obtain a result of hypoellipticity in these spaces. 
Marco Cappiello, Stevan Pilipovic, Bojan Prangoski
math.AP