  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.
