Yassi, Annalee, Tord Kjellström, Theo de Kok, and Tee L. Guidotti. "Risk Assessment." Basic Environmental Health. : Oxford University Press, 2001-05-17. Oxford Scholarship Online. 2009-09-01. Date Accessed 23 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195135589.001.0001/acprof-9780195135589-chapter-3>.
Yassi, A., Kjellström, T., Kok, T., & Guidotti, T.(2001-05-17). Risk Assessment. In Basic Environmental Health. : Oxford University Press. Retrieved 23 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195135589.001.0001/acprof-9780195135589-chapter-3.
Yassi, Annalee, Tord Kjellström, Theo de Kok, and Tee L. Guidotti. "Risk Assessment." In Basic Environmental Health. : Oxford University Press, 2001-05-17. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195135589.001.0001/acprof-9780195135589-chapter-3.
Yassi A, Kjellström T, Kok Td, Guidotti TL. Risk Assessment. In: Yassi A, Kjellström T, de Kok T, Guidotti T. Basic Environmental Health. Oxford University Press; 2001. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195135589.001.0001/acprof-9780195135589-chapter-3. Accessed May 23, 2013.