Cita APA (7a ed.)

Stephenson, H., Hughes, J., & Dummett, P. (2013). Life: Intermediate [B1+]. National Geographic Learning : Heinle Cengage Learning.

Cita Chicago Style (17a ed.)

Stephenson, Helen, John Hughes, y Paul Dummett. Life: Intermediate [B1+]. Andover: National Geographic Learning : Heinle Cengage Learning, 2013.

Cita MLA (9a ed.)

Stephenson, Helen, et al. Life: Intermediate [B1+]. National Geographic Learning : Heinle Cengage Learning, 2013.