"Google Ngram Viewer - Google Books" (Information), Books.Google.com, December 16, 2010, webpage: G-Ngrams-info: notes bigrams and use of quotes for words with apostrophes.
"Google Books Ngram Viewer - University at Buffalo Libraries", Lib.Buffalo.edu, 22 August 2011, webpage: Buf497Archivado el 2 de julio de 2013 en Wayback Machine.
Pechenick, Eitan Adam; Danforth, Christopher M.; Dodds, Peter Sheridan; Barrat, Alain (7 de octubre de 2015). «Characterizing the Google Books Corpus: Strong Limits to Inferences of Socio-Cultural and Linguistic Evolution». PLOS ONE10 (10): e0137041. doi:10.1371/journal.pone.0137041.
"Google's Ngram Viewer: A time machine for wordplay", Cnet.com, 17 December 2010, webpage: CN93Archivado el 23 de enero de 2014 en Wayback Machine.
"Google Books Ngram Viewer - University at Buffalo Libraries", Lib.Buffalo.edu, 22 August 2011, webpage: Buf497Archivado el 2 de julio de 2013 en Wayback Machine.