1. Bocska, S. (2012, September). Gamification pitfalls: Badge fatigue and loyalty backlash. Gamification. Retrieved from http://www.gamification.co/2012/09/12/gamification-pitfalls-badge-fatigue-and-loyalty-backlash/
2. Bunchball. (2010). Gamification 101: An introduction of the use of game mechanics to influence behavior. Retrieved from http://www.bunchball.com/sites/default/files/downloads/gamification101.pdf
3. Deterding, S., Sicart, M., Nacke, L., O’Hara, K., & Dixon, D. (2011, May). Gamification. using game-design elements in non-gaming contexts. In CHI'11 Extended Abstracts on Human Factors in Computing Systems (pp. 2425-2428). ACM.
4. Ferriman, J. (2014). Successful gamification case studies. Learndash. Retrieved from http://www.learndash.com/successful-gamification-case-studies