  We review the Euclidean path-integral formulation of the nucleon hadronic
tensor and classify the gauge invariant and topologically distinct insertions
in terms of connected and disconnected insertions and also in terms of leading
and higher-twist contributions in the DIS region. Converting the Euclidean
hadronic tensor back to the Minkowski space requires solving an inverse problem
of the Laplace transform. We have investigated several inverse algorithms and
studied the pros and cons of each. We show a result with a relatively large
momentum transfer ($Q^2 \sim 4\, {\rm GeV^2}$) to suppress the elastic
scattering and reveal the contributions from the resonance and inelastic region
of the neutrino-nucleon scattering. For elastic scattering, the hadronic tensor
is the the product of the elastic form factors for the two corresponding
currents. We checked numerically for the case of two charge vector currents
($V_4$) with the electric form factor calculated from the three-point function
and found they agree within errors.
