Deterding, S., Dixon, D., Khaled, R., & Nacke, L. (2011). From game design elements to gamefulness: Defining Gamification. ACM.
Chicago Style (17th ed.) CitationDeterding, Sebastian, Dan Dixon, Rilla Khaled, and Lennart Nacke. From Game Design Elements to Gamefulness: Defining Gamification. Tampere, Finland: ACM, 2011.
MLA (9th ed.) CitationDeterding, Sebastian, et al. From Game Design Elements to Gamefulness: Defining Gamification. ACM, 2011.
Warning: These citations may not always be 100% accurate.