The Secret Benefit of Accessibility, Part 2: A Higher Search Engine Ranking
http://www.webcredible.co.uk/user-friendly-resources/web-accessibility/web-accessibility-seo.shtml

Moss, Trenton
Webcredible
2004

Abstract:

One of the lesser-known benefits of web accessibility is the fact that a website more accessible to people is also more accessible to search engines. This article outlines the ways the two areas overlap.