Hilton III, John Levi, Neil Lutz, and David Wiley. “Examining the Reuse of Open Textbooks”. The International Review of Research in Open and Distributed Learning 13, no. 2 (April 13, 2012): 45-58. Accessed January 17, 2020. http://www.irrodl.org/index.php/irrodl/article/view/1137.