RUẬN, Đặng Huy; ỔN, Phùng Văn. Some properties of context free hyper-languages. <b>Journal of Computer Science and Cybernetics</b>, <i>[S. l.]</i>, v. 16, n. 2, p. 5–8, 2013. DOI: 10.15625/1813-9663/16/2/2866. Disponível em: https://jcc.vast.vn/jcc/article/view/2866. Acesso em: 5 nov. 2025.