e choice of frequency-weighted observability
          Grammian as follows:
          = 'S': choice corresponding to a combination method [4]
                 of the approaches of Enns [1] and Lin-Chiu [2,3];
          = 'E': choice corresponding to the stability enhanced
                 modified combination method of [4].

  WEIGHT  CHARACTER*1
          Specifies the type of frequency weighting, as follows:
          = 'N':  no weightings are used (V = I, W = I);
          = 'L':  only left weighting V i