@article{GDZPPN00243606X, title = {A Class of Globally Hypoelliptic Operators on the Torus.}, journal = {Mathematische Zeitschrift}, volume = {202}, year = {1989}, pages = {1-12}, zbl = {0644.35027}, url = {http://dml.mathdoc.fr/item/GDZPPN00243606X} }
Yoshino, Masafumi. A Class of Globally Hypoelliptic Operators on the Torus.. Mathematische Zeitschrift, Tome 202 (1989) pp. 1-12. http://gdmltest.u-ga.fr/item/GDZPPN00243606X/