Pointwise estimates for Green's kernel of a mixed boundary value problem   to the Stokes system in a polyhedral cone
  The paper deals with a mixed boundary value problem for the Stokes system in a polyhedral cone. Here different boundary conditions (in particular, Dirichlet, Neumann, free surface conditions) are prescribed on the sides of the polyhedron. The authors obtain regularity results for weak solutions in weighted $L_2$ Sobolev spaces and prove point estimates of Green's matrix. 
Vladimir G. Maz'ya, Juergen Rossmann