The Relation Between the Differentiability of Solution and Lower-order Terms of the Cauchy Problem for a Class of Weakly Hyperbolic Equations with Singular Coefficients. Journal of Partial Differential Equations, [S. l.], v. 4, n. 1, p. 45–56, 1991. Disponível em: https://www.global-sci.com/index.php/jpde/article/view/3672. Acesso em: 5 dec. 2025.