Cita APA (7a ed.)

Ferree, T., Sanabria, K., Boyd, F. A., & Numrich, C. (1998). Northstar: Focus on listening and speaking : high intermediate. Longman.

Cita Chicago Style (17a ed.)

Ferree, Tess, Kim Sanabria, Frances Armstrong Boyd, y Carol Numrich. Northstar: Focus on Listening and Speaking : High Intermediate. New York: Longman, 1998.

Cita MLA (9a ed.)

Ferree, Tess, et al. Northstar: Focus on Listening and Speaking : High Intermediate. Longman, 1998.