MARGARYAN, V.; GHAZARYAN, H. Almost hypoelliptic operators with constant powers. Eurasian Mathematical Journal, [S. l.], v. 6, n. 4, p. 29–43, 2015. Disponível em: https://emj.enu.kz/index.php/main/article/view/621. Acesso em: 9 oct. 2025.