@article{JLT_2005_15_2_JLT_2005_15_2_a3,
     author = {W. A. d. Graaf },
     title = {Constructing {Homomorphisms} between {Verma} {Modules}},
     journal = {Journal of Lie theory},
     pages = {415--428},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {2005},
     url = {http://geodesic.mathdoc.fr/item/JLT_2005_15_2_JLT_2005_15_2_a3/}
}