APA (7th ed.) Citation

Twain, M., & De Voto, B. (1977). The portable Mark Twain [as printed]. Penguin Books.

Chicago Style (17th ed.) Citation

Twain, Mark, and Bernard De Voto. The Portable Mark Twain [as Printed]. New York: Penguin Books, 1977.

MLA (9th ed.) Citation

Twain, Mark, and Bernard De Voto. The Portable Mark Twain [as Printed]. Penguin Books, 1977.