@article{1200929544,
author = {Morimoto, Yoshinori},
title = {A criterion for hypoellipticity of second order differential operators},
journal = {Osaka J. Math.},
volume = {24},
number = {1},
year = {1987},
pages = { 651-675},
language = {en},
url = {http://dml.mathdoc.fr/item/1200929544}
}
Morimoto, Yoshinori. A criterion for hypoellipticity of second order differential operators. Osaka J. Math., Tome 24 (1987) no. 1, pp. 651-675. http://gdmltest.u-ga.fr/item/1200929544/