APA (7th ed.) Citation
Gaarder, J., & Moller, P. (1995). Sophie's world: A novel about the history of philosophy. Phoenix.
Chicago Style (17th ed.) Citation
Gaarder, Jostein, and Paulette Moller. Sophie's World: A Novel About the History of Philosophy. London: Phoenix, 1995.
MLA (9th ed.) Citation
Gaarder, Jostein, and Paulette Moller. Sophie's World: A Novel About the History of Philosophy. Phoenix, 1995.
Warning: These citations may not always be 100% accurate.