SPARR, Gunnar. A new proof of Löwner’s theorem on monotone matrix functions. Mathematica Scandinavica, Berkeley, CA, United States, v. 47, p. 266–274, 1980. DOI: 10.7146/math.scand.a-11889. Disponível em: https://journals.msp.org/mscand/article/view/1758. Acesso em: 25 jul. 2026.