  We show how the operator product expansion evaluated in the approximation of
ignoring gluons leads to the covariant formulation of the quark parton model.
We discuss the connection with other formulations and show how the free quark
model prediction, $g_2=0$, changes smoothly into the Wandzura-Wilczek (WW)
relation for quark masses small relative to the nucleon mass. Previous
contradictory parton model predictions are shown to follow from an inconsistent
treatment of the mass shell conditions. The description is extended to include
quark mass corrections.
