1. Class differences: Online education in the United States, 2010;Allen,2010
2. Changing course: Ten years of tracking online education in the United States;Allen,2013
3. Factors influencing completion and noncompletion of community college online courses;Aragon;American Journal of Distance Education,2008
4. Competing explanations of undergraduate noncompletion;Attewell;American Educational Research Journal,2011
5. Development of a self-directed learning instrument for use in work environments;Bartlett;Journal of Vocational Education Research,1999