Darwin, C., Barrett, P. H., & Freeman, R. B. (1989). The effects of cross and self fertilization in the vegetable kingdom. Pickering.

Darwin, Charles, Paul H. Barrett, and R. B. Freeman. The Effects of Cross and Self Fertilization in the Vegetable Kingdom. London: Pickering, 1989.

Darwin, Charles, et al. The Effects of Cross and Self Fertilization in the Vegetable Kingdom. Pickering, 1989.