The Boundedness Below of $2×2$ Upper Triangular Linear Relation Matrices. Journal of Mathematical Study, [S. l.], v. 57, n. 1, p. 71–83, 2024. DOI: 10.4208/jms.v57n1.24.04. Disponível em: https://www.global-sci.com/index.php/jms/article/view/13460. Acesso em: 6 dec. 2025.