Tensor Products of Cohen-Macaulay Rings. Solution to a Problem of   Grothendieck
  In this paper we solve a problem, originally raised by Grothendieck, on the transfer of Cohen-Macaulayness to tensor products of algebras over a field. As a prelude to this, we investigate the grade for some specific types of ideals that play a primordial role within the ideal structure of such constructions. 
S. Bouchiba, S. Kabbaj