    -    [ Q   L ]
     R := [       ] &gt;= 0 ,
          [ L'  R ]

  then the pencils

        discrete-time                   continuous-time

  |A   0   B|     |E   0   0|    |A   0   B|     |E   0   0|
  |Q  -E'  L| - z |0  -A'  0| ,  |Q   A'  L| - s |0  -E'  0| ,   (3)
  |L'  0   R|     |0  -B'  0|    |L'  B'  R|     |0   0   0|

  are dichotomic, i.e., they have no eigenvalues on the boundary of
  the stability domain. The above conditions are sufficient for
  regularity of these pencils. A necessar