@article{02215954,
title = {Gevrey hypoellipticity for partial differential equations with characteristics of higher multiplicity.},
journal = {Rendiconti del Seminario Matematico},
volume = {58},
year = {2000},
pages = {435-448},
zbl = {1072.35214},
language = {en},
url = {http://dml.mathdoc.fr/item/02215954}
}
Rodino, Luigi; De Donno, Giuseppe. Gevrey hypoellipticity for partial differential equations with characteristics of higher multiplicity.. Rendiconti del Seminario Matematico, Tome 58 (2000) pp. 435-448. http://gdmltest.u-ga.fr/item/02215954/