BMO estimates for nonvariational operators with discontinuous   coefficients structured on Hormander's vector fields on Carnot groups
  We consider a class of nonvariational linear operators formed by homogeneous left invariant Hormander's vector fields with respect to a structure of Carnot group. The bounded coefficients of the operators belong to "vanishing logarithmic mean oscillation" class with respect to the distance induced by the vector fields (in particular they can be discontinuous). We prove local estimates in "local BMO" spaces intersected with the Lebesgue spaces. Even in the uniformly elliptic case our estimates improve the known results. 
Marco Bramanti, Maria Stella Fanciullo
math.AP