APA (7th ed.) Citation

Walz, S., & Deterding, S. (2015). An Introduction to the Gameful World.

Chicago Style (17th ed.) Citation

Walz, Steffen, and S. Deterding. An Introduction to the Gameful World. 2015.

MLA (9th ed.) Citation

Walz, Steffen, and S. Deterding. An Introduction to the Gameful World. 2015.

Warning: These citations may not always be 100% accurate.