Wiley, David, John Levi Hilton III, Shelley Ellington, and Tiffany Hall. “A Preliminary Examination of the Cost Savings and Learning Impacts of Using Open Textbooks in Middle and High School Science Classes”. The International Review of Research in Open and Distributed Learning 13, no. 3 (June 1, 2012): 262–276. Accessed October 4, 2024. https://www.irrodl.org/index.php/irrodl/article/view/1153.