Cronk, Quentin. "Sporangium to Seed." The Molecular Organography of Plants. : Oxford University Press, 2009-01-29. Oxford Scholarship Online. 2009-05-01. Date Accessed 19 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199550357.001.1/acprof-9780199550357-chapter-5>.
Cronk, Q.(2009-01-29). Sporangium to Seed. In The Molecular Organography of Plants. : Oxford University Press. Retrieved 19 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199550357.001.1/acprof-9780199550357-chapter-5.
Cronk, Quentin. "Sporangium to Seed." In The Molecular Organography of Plants. : Oxford University Press, 2009-01-29. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199550357.001.1/acprof-9780199550357-chapter-5.
Cronk Q. Sporangium to Seed. In: Cronk Q. The Molecular Organography of Plants. Oxford University Press; 2009. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199550357.001.1/acprof-9780199550357-chapter-5. Accessed May 19, 2013.