r. The following matrices
  are computed:

               (  Dout   0  )                   (   0   Vout )
    S12 := Q4' (            ) Q4 and H12 := Q4' (            ) Q4.
               (   0   Fout )                   ( Vout'   0  )

  Then, an orthogonal matrix Q is found such that the eigenvalues
  with strictly negative real parts of the pencil

      (  S11  S12  )     (  H11  H12  )
    a (            ) - b (            )
      (   0   S11' )     (   0  -H11' )

  are moved to the top of this pencil