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Citation for Google Books and Culturomics:

Jean-Baptiste Michel*, Yuan Kui Shen, Aviva Presser Aiden, Adrian Veres, Matthew K. Gray, The Google Books Team, Joseph P. Pickett, Dale Hoiberg, Dan Clancy, Peter Norvig, Jon Orwant, Steven Pinker, Martin A. Nowak, and Erez Lieberman Aiden*.  Quantitative Analysis of Culture Using Millions of Digitized Books. Science 331 (2011) [Published online ahead of print 12/16/2010].