@article{MAN_1993__297_3_165134,
     author = {Jing-song Huang},
     title = {Intertwining differential operators and reducibility of generalized {Verma} modules.},
     journal = {Mathematische Annalen},
     pages = {309--324},
     publisher = {mathdoc},
     volume = {297},
     number = {3},
     year = {1993},
     zbl = {0788.22020},
     url = {http://geodesic.mathdoc.fr/item/MAN_1993__297_3_165134/}
}