Cita APA (7a ed.)

Tompkins, P., & Bird, C. (1991). Secrets of the soil. Viking Arkana.

Cita Chicago Style (17a ed.)

Tompkins, Peter, y Christopher Bird. Secrets of the Soil. London: Viking Arkana, 1991.

Cita MLA (9a ed.)

Tompkins, Peter, y Christopher Bird. Secrets of the Soil. Viking Arkana, 1991.