TY - JOUR AU - I. S. Feshchenko PY - 2011/10/25 Y2 - 2024/03/29 TI - On closeness of the sum of <i>n</i> subspaces of a Hilbert space JF - Ukrains’kyi Matematychnyi Zhurnal JA - Ukr. Mat. Zhurn. VL - 63 IS - 10 SE - Research articles DO - UR - https://umj.imath.kiev.ua/index.php/umj/article/view/2814 AB - We give necessary and sufficient conditions for the sum of subspaces $H_1,..., H_n,, \quad n \geq 2,$ of a Hilbert space $H$ to be a subspace and present various properties of $n$-tuples of subspaces with closed sum. ER -