M. TAMIZH; M. EZHILARASAN. A Survey On Occluded Image Based Captcha For Online Authentication. IIRJET, [S. l.], v. 2, n. Special Issue ICEIET, 2022. Disponível em: http://iirjet.org/index.php/home/article/view/223. Acesso em: 14 apr. 2026.