APA (7th ed.) Citation

Twain, M., Quirk, T., & Cardwell, G. (2002). The innocents abroad. Penguin Books.

Chicago Style (17th ed.) Citation

Twain, Mark, Tom Quirk, and Guy Cardwell. The Innocents Abroad. New York: Penguin Books, 2002.

MLA (8th ed.) Citation

Twain, Mark, et al. The Innocents Abroad. Penguin Books, 2002.