APA (7th ed.) Citation

Hay, R. K. M., & Walker, A. J. (1989). An introduction to the physiology of crop yield. Longman u.a.

Chicago Style (17th ed.) Citation

Hay, Robert K. M., and Andrew J. Walker. An Introduction to the Physiology of Crop Yield. Harlow u.a: Longman u.a, 1989.

MLA (9th ed.) Citation

Hay, Robert K. M., and Andrew J. Walker. An Introduction to the Physiology of Crop Yield. Longman u.a, 1989.