Monica Chew, J. D. Tygar. Image Recognition CAPTCHAs. In Kan Zhang, Yuliang Zheng, editors, Information Security, 7th International Conference, ISC 2004, Palo Alto, CA, USA, September 27-29, 2004, Proceedings. Volume 3225 of Lecture Notes in Computer Science, pages 268-279, Springer, 2004. [doi]
Abstract is missing.