K SIVA NAGALAKSHMI; P.SUMAN PRAKASH; DR S.PREM KUMAR. Confident Multi-Factor Authentication on web application via Captcha Technologies. International Journal of Computer Engineering in Research Trends, [S. l.], v. 2, n. 8, p. 516–522, 2015. Disponível em: https://www.ijcert.org/index.php/ijcert/article/view/206. Acesso em: 18 apr. 2026.