Al-Sharif, Sh., and M. Al-Qahtani. “SOME PROPERTIES OF A NEW KIND OF DOWNWARD SETS IN CERTAIN BANACH SPACES”. Italian Journal of Pure and Applied Mathematics 37 (July 31, 2017): 402–413. Accessed September 16, 2026. https://journals.uniurb.it/index.php/ijpam/article/view/6793.