@article{GDZPPN00234159X,
title = {Solvability for a class of non-homogeneous differential operators on two-step nilpotent groups.},
journal = {Mathematische Annalen},
volume = {305},
year = {1996},
pages = {517-548},
zbl = {0848.43008},
url = {http://dml.mathdoc.fr/item/GDZPPN00234159X}
}
Ricci, Fulvio; Müller, Detlef. Solvability for a class of non-homogeneous differential operators on two-step nilpotent groups.. Mathematische Annalen, Tome 305 (1996) pp. 517-548. http://gdmltest.u-ga.fr/item/GDZPPN00234159X/