10.20 (1986)

In a Chevalley group of rank $\leqslant 6$ over a finite field of order $\leqslant 9$, describe all subgroups of the form $H = \langle H \cap U, H \cap V \rangle$ that are not contained in any proper parabolic subgroup, where $U$ and $V$ are opposite unipotent subgroups.