APA (7th ed.) Citation

Philip Lief Group, Princeton Language Institute, & O'Connor, J. (1994). 21st century guide to pronunciation. Dell.

Chicago Style (17th ed.) Citation

Philip Lief Group, Princeton Language Institute, and Joyce O'Connor. 21st Century Guide to Pronunciation. New York: Dell, 1994.

MLA (9th ed.) Citation

Philip Lief Group, et al. 21st Century Guide to Pronunciation. Dell, 1994.