1. Black, P., Harrison, C., Lee, C., Marshall, B., & Wiliam, C. (2003). Assessment for learning: Putting it into practice. Maidenhead: Open University Press.
2. Blackboard Inc. (2008) Company overview. Retrieved on October 22, 2008, from http://www.blackboard.com/company/
3. Measuring oral proficiency in distance, face-to-face, and blended classrooms.;R.Blake;Language Learning & Technology,2008
4. Exploring the tutor/client conversation: A linguistic analysis.;S. R.Blau;Writing Center Journal,1998
5. Boud, D., & Feletti, G. (1991). The challenge of problem based learning. London: Kogan Page.