@article{GDZPPN002360403,
title = {Singular vectors corresponding to imaginary roots in verma modules over affine Lie algebras.},
journal = {Mathematica Scandinavica},
volume = {67},
year = {1990},
pages = {73-90},
zbl = {0687.17009},
url = {http://dml.mathdoc.fr/item/GDZPPN002360403}
}
Malikow, F. Singular vectors corresponding to imaginary roots in verma modules over affine Lie algebras.. Mathematica Scandinavica, Tome 67 (1990) pp. 73-90. http://gdmltest.u-ga.fr/item/GDZPPN002360403/