Pointwise Multipliers for Sobolev and Besov Spaces of Dominating Mixed   Smoothness
  Under certain restrictions we describe the set of all pointwise multipliers in case of Sobolev and Besov spaces of dominating mixed smoothness. In addition we shall give necessary and sufficient conditions for the case that these spaces form algebras with respect to pointwise multiplication. 
Van Kien Nguyen and Winfried Sickel
math.FA