  We evaluate the differential cross section for the electroproduction of
lepton pairs off a polarized nucleon target in the generalized Bjorken region
to leading power accuracy in hard momentum. We discuss the importance of this
process for phenomenology of generalized parton distributions. A special
attention is given to the sensitivity of physical observables, i.e., diverse
asymmetries, to their dependence on scaling variables that allows to map
directly the functional two-dimensional surface of generalized parton
distributions.
