Feshchenko I. A sufficient condition for the sum of complemented subspaces to be complemented . Dopov. Nac. akad. nauk Ukr. [Internet]. 2024 Mar. 28 [cited 2026 Apr. 30];(1):10-5. Available from: https://nasu-periodicals.org.ua/index.php/dp/article/view/2019-1-2