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: http://fs.unm.edu/NSS2/index.php/111/article/view/493. Acesso em: 4 jun. 2023.