APA (7th ed.) Citation

Philip Lief Group, Princeton Language Institute, & Kipfer, B. A. (1993). 21st-century manual of style. Laurel.

Chicago Style (17th ed.) Citation

Philip Lief Group, Princeton Language Institute, and Barbara Ann Kipfer. 21st-century Manual of Style. New York: Laurel, 1993.

MLA (9th ed.) Citation

Philip Lief Group, et al. 21st-century Manual of Style. Laurel, 1993.