The Fine Structure of Translation Functors
  Let E be a simple finite dimensional representation of a semisimple Lie algebra with extremal weight nu and choose nonzero e in E_{nu}. Let M(tau) be the Verma module with highest weight tau and v_{tau} in M(tau)_{tau} its canonical generator. We investigate the projection of e \otimes v_{tau} in E \otimes M(tau) on the central character chi(tau + nu). This is a rational function in tau and we calculate its poles and zeros. We then apply this result in order to compare translation functors. 
Karen Guenzl