@article{GDZPPN002444690, title = {A non uniqueness result for operators of principle type.}, journal = {Mathematische Zeitschrift}, volume = {220}, year = {1995}, pages = {561-568}, zbl = {0851.35003}, url = {http://dml.mathdoc.fr/item/GDZPPN002444690} }
Baouendi, M.S.; Alinhac, S. A non uniqueness result for operators of principle type.. Mathematische Zeitschrift, Tome 220 (1995) pp. 561-568. http://gdmltest.u-ga.fr/item/GDZPPN002444690/