Chapter 9 Sobolev Spaces and the Variational Formulation of Elliptic Boundary Value Problems in N Dimensions Let CR an open set and. bounded of class c². It is asked To Find MR such that. - Au tusf on r coppres Dy =0 over d DV yorq where f & L² (2) is a given functiona LS normal. and Du the exterior DV derivative of u, that, Duu.V₁ being V the extervor normal unit vector TO DR. 10