Cita APA (7th ed.)

Darwin, C., Barrett, P. H., & Freeman, R. B. (1986). The foundations of the origin of species: Two essays written in 1842 and 1844. Pickering.

Cita Chicago (17th ed.)

Darwin, Charles, Paul H. Barrett, i R. B. Freeman. The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844. London: Pickering, 1986.

Cita MLA (8th ed.)

Darwin, Charles, et al. The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844. Pickering, 1986.