HERNQUIST, Dale Clarke. 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://tidsskrift.dk/math/article/view/12203. Acesso em: 14 aug. 2026.