  We generalize the dressing symmetry construction in mKdV hierarchy. This
leads to non-local vector fields (expressed in terms of vertex operators)
closing a Virasoro algebra. We argue that this algebra realization should play
an important role in the study of 2D integrable field theories and in
particular should be related to the Deformed Virasoro Algebra (DVA) when the
construction is perturbed out of the critical theory.
