1. Wiley, D.A.: Connecting learning objects to instructional design theory: a definition, a metaphor, and a taxonomy. http://reusability.org/read/chapters/wiley.doc (2000). Accessed 12 March 2012
2. Simonson, M., Schlosser, C., Orellana, A.: Distance education research: a review of the literature. J. Comput. High. Educ. 23(2–3), 124–142 (2011)
3. Swan, K.: Learning effectiveness online: what the research tell us. In: Bourne, J., Moore, J.C. (eds.) Elements of quality Online Education, Practice and Direction, vol. 4, pp. 13–45. Needham, MA (2003)
4. Swan, K., Shih, L.F.: On the nature and development of social presence in online course discussions. J. Asynch. Learn. Netw. 9(3), 115–136 (2005)
5. Foreman, J.: Distance learning and synchronous interaction. The technology source archives. http://www.technologysource.org/article/distance_learning_and_synchronous_interaction (2003). Accessed 12 March 2012