The Hypoellipticity and Parametrices for a Class of Nonprincipal Type LPDOs. Journal of Partial Differential Equations, [S. l.], v. 6, n. 4, p. 339–348, 2020. Disponível em: https://global-sci.com/index.php/jpde/article/view/3755. Acesso em: 5 dec. 2025.