APA (7th ed.) Citation

Deterding, S., Dixon, D., Khaled, R., & Nacke, L. (2011). From game design elements to gamefulness: Defining Gamification. ACM.

Chicago Style (17th ed.) Citation

Deterding, Sebastian, Dan Dixon, Rilla Khaled, and Lennart Nacke. From Game Design Elements to Gamefulness: Defining Gamification. Tampere, Finland: ACM, 2011.

MLA (9th ed.) Citation

Deterding, Sebastian, et al. From Game Design Elements to Gamefulness: Defining Gamification. ACM, 2011.