Roberts, R. Michael. "Genetically Modified Organisms for Agricultural Food Production: The Extent of the Art and the State of the Science." Labeling Genetically Modified Food: The Philosophical and Legal Debate. : Oxford University Press, 2008-04-01. Oxford Scholarship Online. 2008-01-01. Date Accessed 18 Jun. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195326864.001.0001/acprof-9780195326864-chapter-2>.
Roberts, R.(2008-04-01). Genetically Modified Organisms for Agricultural Food Production: The Extent of the Art and the State of the Science. In Labeling Genetically Modified Food: The Philosophical and Legal Debate. : Oxford University Press. Retrieved 18 Jun. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195326864.001.0001/acprof-9780195326864-chapter-2.
Roberts, R. Michael. "Genetically Modified Organisms for Agricultural Food Production: The Extent of the Art and the State of the Science." In Labeling Genetically Modified Food: The Philosophical and Legal Debate. : Oxford University Press, 2008-04-01. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195326864.001.0001/acprof-9780195326864-chapter-2.
Roberts RM. Genetically Modified Organisms for Agricultural Food Production: The Extent of the Art and the State of the Science. In: Weirich P. Labeling Genetically Modified Food: The Philosophical and Legal Debate. Oxford University Press; 2008. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195326864.001.0001/acprof-9780195326864-chapter-2. Accessed June 18, 2013.