1. Allen, E. and Seaman, J. (2010). Learning on demand: online education in the United States, 2009. Babson Survey Research Group.
2. Barbour, M.K. and Reeves, T.C. (2009). The reality of virtual schools: a review of the literature. Computers & Education, 52, pp. 402-416.
3. Battey K. (2015) Survey Questions and Answer Types. COO, QuestionPro - http://www.questionpro.com/a/showArticle.do?articleID=survey-questions.
4. Baynton, M. (1992), “Dimensions of control in distance education: a factor analysis”, The American Journal of Distance Education, Vol. 6 No. 2, pp. 17-31.
5. Bringing knowledge within reach.(2005) – eEurope: eLearning, 2005, p. 5 - http://ec.europa.eu/information_society/doc/factsheets/005-e-Learning.pdf.