Richards, J. F. 1990. Land transformation. Pages 163-178 in B. L.Turner, W. C. Clark, and W. B. Meyer, editors. The Earth as transformed by human action. Cambridge University Press, Cambridge, UK.
Diamond, J. M. 1975. The island dilemma: lessons of modern biogeographic studies for the design of nature reserves. Biological Conservation 7:129-146.
The American Journal of Botany provides examples of the citation style recommended for your class, see Literature Cited Instruction (pdf)
Ashton et al., 2007; Brown, 2007; Jackson, 2005, 2008.