ABRAHAMSEN, Trond A. Strict U-Ideals and U-Summands in Banach Spaces. MATHEMATICA SCANDINAVICA, [S. l.], v. 114, n. 2, p. 216–225, 2014. DOI: 10.7146/math.scand.a-17108. Disponível em: https://tidsskrift.dk/math/article/view/17108. Acesso em: 14 aug. 2026.