HERNQUIST, D. C. Smoothly symmetrizable hyperbolic systems of partial differential equations. MATHEMATICA SCANDINAVICA, [S. l.], v. 61, p. 262–275, 1987. DOI: 10.7146/math.scand.a-12203. Disponível em: https://www.mscand.dk/article/view/12203. Acesso em: 30 apr. 2024.