@article{GDZPPN00232573X,
title = {Analytic Hypo-Ellipticity and Propagation of Regularity for a System of Microdifferential Equations with Non-Involutory Characteristics.},
journal = {Mathematische Annalen},
volume = {268},
year = {1984},
pages = {145-168},
zbl = {0535.35012},
url = {http://dml.mathdoc.fr/item/GDZPPN00232573X}
}
Oaku, Toshinori. Analytic Hypo-Ellipticity and Propagation of Regularity for a System of Microdifferential Equations with Non-Involutory Characteristics.. Mathematische Annalen, Tome 268 (1984) pp. 145-168. http://gdmltest.u-ga.fr/item/GDZPPN00232573X/