BHARDWAJ, V. K.; GUPTA, S. On the β-Dual of Banach-Space-Valued Difference Sequence Spaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 65, n. 8, p. 1145–1151, 2013. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2497. Acesso em: 5 dec. 2025.