Higher Twist, $\xi_w$ Scaling, and Effective $LO PDFs$ for Lepton   Scattering in the Few GeV Region
  We use a new scaling variable $\xi_w$, and add low $Q^2$ modifications to GRV98 leading order parton distribution functions such that they can be used to model electron, muon and neutrino inelastic scattering cross sections (and also photoproduction) at both very low and high energies. 
A. Bodek and U. K. Yang