APA (7th ed.) Citation

Bird, S., Klein, E., & Loper, E. (2009). Natural Language Processing with Python (1st edition.). O'Reilly Media, Inc..

Chicago Style (17th ed.) Citation

Bird, Steven, Ewan Klein, and Edward Loper. Natural Language Processing with Python. 1st edition. O'Reilly Media, Inc., 2009.

MLA (9th ed.) Citation

Bird, Steven, et al. Natural Language Processing with Python. 1st edition. O'Reilly Media, Inc., 2009.