Heydari, F., and D. Behmardi. “A NOTE ON NON-FRAGMENTABLE SUBSPACE OF \(\ell_ ꝏ^{c}\)(Γ)”. Italian Journal of Pure and Applied Mathematics, vol. 33, Dec. 2014, pp. 133-8, https://journals.uniurb.it/index.php/ijpam/article/view/6285.