Christos Fidas, Artemios G. Voyiatzis, Nikolaos M. Avouris. On the necessity of user-friendly CAPTCHA. In Desney S. Tan, Saleema Amershi, Bo Begole, Wendy A. Kellogg, Manas Tungare, editors, Proceedings of the International Conference on Human Factors in Computing Systems, CHI 2011, Vancouver, BC, Canada, May 7-12, 2011. pages 2623-2626, ACM, 2011. [doi]
Abstract is missing.