HUY, Nguyen Xuan. A labelling operator and relational operations. <b>Journal of Computer Science and Cybernetics</b>, <i>[S. l.]</i>, v. 1, n. 3, p. 1–7, 2015. DOI: 10.15625/1813-9663/1/3/6687. Disponível em: https://jcc.vast.vn/jcc/article/view/6687. Acesso em: 4 nov. 2025.