Williams, Ernest H. "Epilogue." The Nature Handbook: A Guide to Observing the Great Outdoors. : Oxford University Press, 2005-04-14. Oxford Scholarship Online. 2007-09-01. Date Accessed 19 Jun. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195179293.001.0001/acprof-9780195179293-chapter-15>.
Williams, E.(2005-04-14). Epilogue. In The Nature Handbook: A Guide to Observing the Great Outdoors. : Oxford University Press. Retrieved 19 Jun. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195179293.001.0001/acprof-9780195179293-chapter-15.
Williams, Ernest H. "Epilogue." In The Nature Handbook: A Guide to Observing the Great Outdoors. : Oxford University Press, 2005-04-14. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195179293.001.0001/acprof-9780195179293-chapter-15.
Williams EH. Epilogue. In: Williams Jr. EH. The Nature Handbook: A Guide to Observing the Great Outdoors. Oxford University Press; 2005. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195179293.001.0001/acprof-9780195179293-chapter-15. Accessed June 19, 2013.