Koszul duality for modules over Lie algebras

Let g be a reductive Lie algebra over afield of characteristic zero. Suppose that D acts on a complex of vector spaces M-. by i(lambda) and L-lambda, which satisfy the same identities that contraction and Lie derivative do for differential forms. Out of this data one defines the cohomology of the invariants and the equivariant cohomology of M-.. We establish Koszul duality between them.