Monica Chew, Henry S. Baird. BaffleText: a human interactive proof. In Tapas Kanungo, Elisa H. Barney Smith, Jianying Hu, Paul B. Kantor, editors, Document Recognition and Retrieval X, 22-23 January 2003, Santa Clara, California, USA, Proceedings. Volume 5010 of SPIE Proceedings, pages 305-316, SPIE, 2003. [doi]
Abstract is missing.