CICOGNANI, M.; HIROSAWA, F. On the Gevrey well-posedness for second order strictly hyperbolic Cauchy problems under the influence of the regularity of the coefficients. MATHEMATICA SCANDINAVICA, [S. l.], v. 102, n. 2, p. 283–304, 2008. DOI: 10.7146/math.scand.a-15063. Disponível em: https://www.mscand.dk/article/view/15063. Acesso em: 3 may. 2024.