s not a maximal row rank or when a certain balance between
  relative and absolute approximation errors is desired. For
  increasingly large values of BETA, the obtained reduced system
  assymptotically approaches that computed by using the
  Balance & Truncate or Singular Perturbation Approximation methods.

  Note: conj(G)  denotes either G'(-s) for a continuous-time system
        or G'(1/z) for a discrete-time system.
        inv(G) is the inverse of G.

  The following procedure is used to reduce a giv