APA Style

Thaler, R, H., Sunstein, C, R. (2009). Nudge : improving decisions about health, wealth, and happiness . New York: Penguin Books.

MLA Style

Thaler, Richard, H.., Sunstein, Cass, R.. "Nudge : improving decisions about health, wealth, and happiness". New York: Penguin Books, 2009. Text.