ISHIBASHI, AYAKA; SATO, YUICHI; IWATA, SHIGEKI. NP-completeness of two pencil puzzles: Yajilin and Country Road. Utilitas Mathematica , [S. l.], v. 88, 2012. Disponível em: https://utilitasmathematica.com/index.php/Index/article/view/863. Acesso em: 27 oct. 2026.