"This new interface for Google Books allows you to search more than 155 billion (155,000,000,000) words in more than 1.3 million books of American English from 1810-2009 (including 62 billion words from 1980-2009). Although this "corpus" is based on Google Books data, it is not an official product of Google or Google Books, but rather it was created by Mark Davies, Professor of Linguistics at Brigham Young University, and it is related to other large corpora that we have created."

http://googlebooks.byu.edu/

(T)