Cita APA (7a ed.)

Crystal, D., & Davy, D. (1979). Advanced conversational English. Longman.

Cita Chicago Style (17a ed.)

Crystal, David, y Derek Davy. Advanced Conversational English. London: Longman, 1979.

Cita MLA (9a ed.)

Crystal, David, y Derek Davy. Advanced Conversational English. Longman, 1979.