1. AdamsE. (2009). Fundamentals of Game Design (2nd ed.). Berkeley, CA: New Riders Press.
2. Theoretical propositions of life-span developmental psychology: On the dynamics between growth and decline.
3. Bosmans, D., & Maskell, P. (2012). Videogames in Europe: 2012 Consumer Study. ISFE & Ipsos MediaCT. Retrieved from http://www.isfe.eu/industry-facts/statistics
4. Exploring the Next Generation of Older Gamers: Middle-Aged Gamers
5. Charmaz, K. (2006). Constructing Grounded Theory. Retrieved from http://books.google.be/books?id=w2sDdv-S7PgC&printsec=frontcover&dq=0761973524&source=bl&ots=pZrr4YGGeu&sig=R7pxfUS9Hz43Qctzt1Z_AUPeZYs&hl=nl&ei=3MFETP2VFNW94gaHtqTPDg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBUQ6AEwAA#v=onepage&q&f=false