12 September 2008
Vol 321, Issue 5895

About The Cover

Cover image expansion

COVER Millions of books written before the computer era are being digitized for preservation. Because the ink has faded, optical character recognition software cannot decipher many words. Through a repurposing of an existing online security technology called CAPTCHA, these words are being manually transcribed by millions of Web users. See page 1465. Photo: Joshua Franzos