Sobhy El-sayed IBRAHIM. The Regularly Solvable Operators with Their Products and Spectra in Direct Sum Spaces. Novel Research Aspects in Mathematical and Computer Science Vol. 2, [S. l.], p. 124–146, 2022. DOI: 10.9734/bpi/nramcs/v2/6147F. Disponível em: https://stm.bookpi.org/NRAMCS-V2/article/view/6796. Acesso em: 4 jun. 2026.