23 pages, 5 figures; added several corrections according to the
  published erratum except for Eq.(6) (it was correct in the original paper)
  and with additional correction in Eq.(96)
  [$\bar{\mathbf{G}}(...)\mathbf{P}_i^s -\bar{\mathbf{G}}^s(...)\mathbf{P}_i^p$
  instead of $(\bar{\mathbf{G}}(...) - \bar{\mathbf{G}}^s(...))\mathbf{P}_i^s$]