1. H. S. Baird, “Document Image Defect Models,” in H. S. Baird, H. Bunke, and K. Yamamoto Eds., Structured Document Image Analysis, Springer-Verlag: New York, 1992, pp. 546–556.
2. M. Blum, L. A. von Ahn, and J. Langford, The CAPTCHA Project, “Completely Automatic Public Turing Test to tell Computers and Humans Apart,”
http://www.captcha.net
, Dept. of Computer Science, Carnegie-Mellon Univ., and personal communications, November, 2000.
3. D. P. Baron, “eBay and Database Protection,” Case No. P-33, Case Writing Office, Stanford Graduate School of Business, 518 Memorial Way, Stanford Univ., Stanford, CA 94305-5015, 2001.
4. Alta Vista’s “Add-URL” site: altavista.com/sites/addurl/newurl, protected by the earliest known CAPTCHA.
5. A. L. Coates, H. S. Baird, R. Fateman, “Pessimal Print: a Reverse Turing Test,” Proc., IAPR 6th Intl. Conf. on Document Analysis and Recognition, Seattle, WA, September 10–13, 2001, pp. 1154–1158.