«3.2 History of Books». 3.2 History of Books | Understanding Media and Culture: An Introduction to Mass Communication. open.lib.umn.edu (em inglês). [S.l.]: University of Minnesota Libraries Publishing edition, 2016. This edition is adapted from a work originally produced in 2010 by a publisher who has requested that it not receive attribution. 2016. Consultado em 11 de abril de 2018
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«Early Writing». hrc.utexas.edu. Consultado em 11 de abril de 2018. Arquivado do original em 6 de janeiro de 2018