  Lattice calculations could boost our understanding of Deep Inelastic
Scattering by evaluating moments of the Nucleon Structure Functions. To this
end we study the product of electromagnetic currents between quark states. The
Operator Product Expansion (OPE) decomposes it into matrix elements of local
operators (depending on the quark momenta) and Wilson coefficients (as
functions of the larger photon momenta). For consistency with the matrix
elements, we evaluate a set of Wilson coefficients non-perturbatively, based on
propagators for numerous momentum sources, on a 24^3 x 48 lattice. The use of
overlap quarks suppresses unwanted operator mixing and lattice artifacts.
Results for the leading Wilson coefficients are extracted by means of Singular
Value Decomposition.
