@article{1195511841,
author = {Gramchev, Todor and Popivanov, Petar and Yoshino, Masafumi},
title = {Global solvability and hypoellipticity on the torus for a class of differential operators withvariable coefficients},
journal = {Proc. Japan Acad. Ser. A Math. Sci.},
volume = {68},
number = {10},
year = {1992},
pages = { 53-57},
language = {en},
url = {http://dml.mathdoc.fr/item/1195511841}
}
Gramchev, Todor; Popivanov, Petar; Yoshino, Masafumi. Global solvability and hypoellipticity on the torus for a class of differential operators withvariable coefficients. Proc. Japan Acad. Ser. A Math. Sci., Tome 68 (1992) no. 10, pp. 53-57. http://gdmltest.u-ga.fr/item/1195511841/