FESHCHENKO, I. . A sufficient condition for the sum of complemented subspaces to be complemented . Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 1, p. 10–15, 2024. DOI: 10.15407/dopovidi2019.01.010. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/2019-1-2. Acesso em: 30 apr. 2026.