@Article{JPDE-6-339, author = {Jiang Yaping}, title = {The Hypoellipticity and Parametrices for a Class of Nonprincipal Type LPDOs}, journal = {Journal of Partial Differential Equations}, year = {1993}, volume = {6}, number = {4}, pages = {339--348}, abstract = { In this paper, we employ the method of increment operators, by means of the left invariant operators £^{v,s} on nilpotent Lie group G^{d_1+d_2} and the calculus of v- &PsiDOs, to discuss the hypoellipticity for a class of nonprincipal type LPDOs £ on a d_1 + d_2 dimensional manifold M. For those hypoelliptic £ we also construct their parametrices.}, issn = {2079-732X}, doi = {https://doi.org/}, url = {http://global-sci.org/intro/article_detail/jpde/5720.html} }