@article{GDZPPN002208504,
title = {A new criterion for local non-solvability of homogeneous left invariant differential operators on nilpotent Lie groups.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {416},
year = {1991},
pages = {207-219},
zbl = {0716.22003},
url = {http://dml.mathdoc.fr/item/GDZPPN002208504}
}
Müller, D. A new criterion for local non-solvability of homogeneous left invariant differential operators on nilpotent Lie groups.. Journal für die reine und angewandte Mathematik, Tome 416 (1991) pp. 207-219. http://gdmltest.u-ga.fr/item/GDZPPN002208504/