  Average effective two-body interaction matrix elements in the s-d shell have
been extracted, from data on experimentally measured isospin centroids, by
combining the recently derived new sum rules equations for pick-up reactions
with similar known equations for stripping reactions performed on general
multishell target states. Using this combination of stripping and pick-up
equations, the average effective matrix elements for the shells, 1d^2_5/2,
2s^2_1/2 and 1d^2_3/2 respectively have been obtained. A new feature of the
present work is that the restriction imposed in earlier works on target states,
that it be populated only by active neutrons has now been abandoned.
