There you go: https://text-analysis.googlecode.com/files/luhn58.pdf‎ https://text-analysis.googlecode.com/files/luhn58.pdf‎ http://dl.acm.org/citation.cfm?id=1

There you go: https://text-analysis.googlecode.com/files/luhn58.pdf‎ https://text-analysis.googlecode.com/files/luhn58.pdf‎ http://dl.acm.org/citation.cfm?id=1662360 http://dl.acm.org/citation.cfm?id=1662360