  (       22 )       (       22 )

  be the given matrix pair in generalized Schur form, where
  initially A   and B   are the first diagonal elements.
             11      11
  An attempt is made to compute the transformation matrices X and Y
  of the form

         ( I   V )       ( I   W )
     X = (       ),  Y = (       )                               (1)
         ( 0   I )       ( 0   I )

  (partitioned as A and B ), so that (' denotes conjugate-transpose)

              ( A     0  )            ( B  