of the transfer-function matrix G
  of the system (A,B,C,D). G must not have poles on the imaginary
  axis, for a continuous-time system, or on the unit circle, for
  a discrete-time system. If the H2-norm is computed, the system
  must be stable.

</PRE>
<A name="Specification"><B><FONT SIZE="+1">Specification</FONT></B></A>
<PRE>
      DOUBLE PRECISION FUNCTION AB13BD( DICO, JOBN, N, M, P, A, LDA,
     $                                  B, LDB, C, LDC, D, LDD, NQ, TOL,
     $                              