Parton distributions in the presence of target mass corrections
  We study the consistency of parton distribution functions in the presence of target mass corrections (TMCs) at low Q^2. We review the standard operator product expansion derivation of TMCs in both x and moment space, and present the results in closed form for all unpolarized structure functions and their moments. To avoid the unphysical region at x > 1 in the standard TMC analysis, we propose an expansion of the target mass corrected structure functions order by order in M^2/Q^2, and assess the convergence properties of the resulting forms numerically. 
F. M. Steffens, M. D. Brown, W. Melnitchouk, S. Sanches
hep-ph nucl-th