Cita APA (7a ed.)

O'Connor, J. D., Fletcher, C., & Kenworthy, J. (1991). Sounds english: A pronunciation practice book. Longman.

Cita Chicago Style (17a ed.)

O'Connor, Joseph Desmond, Clare Fletcher, y Joanne Kenworthy. Sounds English: A Pronunciation Practice Book. Essex: Longman, 1991.

Cita MLA (8a ed.)

O'Connor, Joseph Desmond, et al. Sounds English: A Pronunciation Practice Book. Longman, 1991.