1. Ahonen , T. 2007 Putting 2.7 billion in context: mobile phone users Wireless Watch Community Website http://communities-dominate.blogs.com/brands/2007/01/putting_27_bill.html
2. Virtual communities and their importance for informal learning;Andreatos;International Journal of Computer, Communication & Control,2007
3. Designing motivational learning systems in distance education;Balaban-Sali;Turkish Online Journal of Distance Education,2008
4. Burgstahler , S. 2011 Universal design of instruction (UDI): definitions, principles, guidelines, and examples http://www.washington.edu/doit/Brochures/Academics/instruction.html