VỴ, N. V.; ĐỨC, Đặng V.; ĐỨC, N. M. A relational algebraical model of object oriented systems. Journal of Computer Science and Cybernetics, [S. l.], v. 21, n. 3, p. 261–270, 2012. DOI: 10.15625/1813-9663/21/3/1250. Disponível em: https://vjs.ac.vn/index.php/jcc/article/view/1250. Acesso em: 3 may. 2024.