HA-stable eigenvalues (NU+NS = N),
          NR is set as follows: if ORDSEL = 'F', NR is equal to
          NU+MIN(MAX(0,NR-NU),NMIN), where NR is the desired order
          on entry, and NMIN is the order of a minimal realization
          of the ALPHA-stable part of the given system; NMIN is
          determined as the number of Hankel singular values greater
          than NS*EPS, where EPS is the machine precision
          (see LAPACK Library Routine DLAMCH);
          if ORDSEL = 'A', NR is the sum 