Cita APA (7a ed.)

Burbidge, N., Gray, P., & Levy, S. Letters (2a ed.).

Cita Chicago Style (17a ed.)

Burbidge, Nicky, Peta Gray, y Sheila Levy. Letters. 2a ed.

Cita MLA (8a ed.)

Burbidge, Nicky, et al. Letters. 2a ed.