e continuous-time Lyapunov equation

     AQ'*X + X*AQ + CQ'*CQ = 0.

  If DICO = 'D', then the l2-norm of G is computed as

     NORM2(G) = NORM2(Q) = SQRT(TRACE(BQ'*X*BQ+DQ'*DQ)),

  where X satisfies the discrete-time Lyapunov equation

     AQ'*X*AQ - X + CQ'*CQ = 0.

</PRE>
<A name="References"><B><FONT SIZE="+1">References</FONT></B></A>
<PRE>
  [1] Varga A.
      On computing 2-norms of transfer-function matrices.
      Proc. 1992 ACC, Chicago, June 1992.

  [2] Varga A.
      A Schur method for comp