@article{1200783225,
author = {Morioka, Tatsushi},
title = {Hypoellipticity for semi-elliptic operators which degenerate on hypersurface},
journal = {Osaka J. Math.},
volume = {28},
number = {1},
year = {1991},
pages = { 563-578},
language = {en},
url = {http://dml.mathdoc.fr/item/1200783225}
}
Morioka, Tatsushi. Hypoellipticity for semi-elliptic operators which degenerate on hypersurface. Osaka J. Math., Tome 28 (1991) no. 1, pp. 563-578. http://gdmltest.u-ga.fr/item/1200783225/