APA (7th ed.) Citation

Tibbetts, A. M., & Tibbetts, C. (1978). What's happening to American English? Scribner.

Chicago Style (17th ed.) Citation

Tibbetts, A. M., and Charlene Tibbetts. What's Happening to American English? New York: Scribner, 1978.

MLA (9th ed.) Citation

Tibbetts, A. M., and Charlene Tibbetts. What's Happening to American English? Scribner, 1978.