With the failure of simple RPA calculations to describe the data, as
mentioned in sections 
and , several
different theoretical corrections were forthcoming. For the most part,
these theories in some way adjusted the parameters of the particle-hole
potential given in equation . The three primary correction
techniques proposed are described below. None were completely successful
in describing the
data at 
MeV, but all offer methods by which expected
longitudinal to transverse ratio can be suppressed [Lut93].