Cita APA (7a ed.)

Percil, J., & Gray, J. (1988). Prospects: An advanced course teacher's book. Penguin Books.

Cita Chicago Style (17a ed.)

Percil, John, y Joanna Gray. Prospects: An Advanced Course Teacher's Book. London: Penguin Books, 1988.

Cita MLA (9a ed.)

Percil, John, y Joanna Gray. Prospects: An Advanced Course Teacher's Book. Penguin Books, 1988.