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7I. Elaine Allen (2004).Entering the Mainstream: The Quality and Extent of Online Education in the United States, 2003 and 2004.http://www.sloan -c.org/resources/entering_mainstream.pdf,2005.12.30.
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9I. Elaine Allen (2005).Making the Grade: Online Education in the United States, 2006. www.sloan -c.org/publications/survey/pdf/ making_t he_grade.pdf.
