@article{IM_1992__110_2_144066,
     author = {R. Richardson and G. R\"ohrle and R. Steinberg},
     title = {Parabolic subgroups with {Abelian} unipotent radical.},
     journal = {Inventiones mathematicae},
     pages = {649--671},
     publisher = {mathdoc},
     volume = {110},
     number = {2},
     year = {1992},
     zbl = {0786.20029},
     url = {http://geodesic.mathdoc.fr/item/IM_1992__110_2_144066/}
}