@article{JLT_2003_13_1_JLT_2003_13_1_a11,
     author = {C. Stroppel },
     title = {Homomorphisms and {Extensions} of {Principal} {Series} {Representations}},
     journal = {Journal of Lie theory},
     pages = {193--212},
     publisher = {mathdoc},
     volume = {13},
     number = {1},
     year = {2003},
     url = {http://geodesic.mathdoc.fr/item/JLT_2003_13_1_JLT_2003_13_1_a11/}
}