BONDER, Elmer. The approximation property for a pair of Banach spaces. Mathematica Scandinavica, Berkeley, CA, United States, v. 57, p. 375–385, 1985. DOI: 10.7146/math.scand.a-12123. Disponível em: https://journals.msp.org/mscand/article/view/1545. Acesso em: 25 jul. 2026.