@inproceedings{CHI-2009-BighamC,
	author        = "Jeffrey P. Bigham and Anna Cavender",
	booktitle     = "{Proceedings of the 27th ACM SIGCHI Conference on Human Factors in Computing Systems}",
	doi           = "10.1145/1518701.1518983",
	isbn          = "978-1-60558-246-7",
	pages         = "1829--1838",
	publisher     = "{ACM}",
	title         = "{Evaluating existing audio CAPTCHAs and an interface optimized for non-visual use}",
	year          = 2009,
}