/PRE>
<A name="References"><B><FONT SIZE="+1">References</FONT></B></A>
<PRE>
  [1] Ghavimi, A.R. and Laub, A.J.
      Backward error, sensitivity, and refinement of computed
      solutions of algebraic Riccati equations.
      Numerical Linear Algebra with Applications, vol. 2, pp. 29-49,
      1995.

  [2] Higham, N.J.
      Perturbation theory and backward error for AX-XB=C.
      BIT, vol. 33, pp. 124-136, 1993.

  [3] Petkov, P.Hr., Konstantinov, M.M., and Mehrmann, V.
      DGRSVX and DMSRIC: Fortran