BRENNER, Philip. Initial Value Problems in $L_p$ for Systems with Variable Coefficients. Mathematica Scandinavica, Berkeley, CA, United States, v. 30, p. 141–149, 1972. DOI: 10.7146/math.scand.a-11070. Disponível em: https://journals.msp.org/mscand/article/view/2253. Acesso em: 25 jul. 2026.