FU YUHUA. Negating Four Color Theorem with Neutrosophy and Quad-stage Method. Neutrosophic Sets and Systems, [S. l.], v. 8, p. 59–62, 2015. Disponível em: https://fs.unm.edu/nss8/index.php/111/article/view/493.. Acesso em: 17 jun. 2025.