CABRAL, Rodrigo A. H. M. Strongly elliptic operators and exponentiation of operator Lie algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 127, n. 2, p. 264–286, 2021. DOI: 10.7146/math.scand.a-126020. Disponível em: https://journals.msp.org/mscand/article/view/151. Acesso em: 24 jul. 2026.