Orangutans: Geographic Variation in Behavioral Ecology and Conservation. : Oxford University Press, 2008-12-11. Oxford Scholarship Online. 2009-05-01. Date Accessed 18 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199213276.001.0001/acprof-9780199213276>.
(2008-12-11). Orangutans: Geographic Variation in Behavioral Ecology and Conservation. : Oxford University Press. Retrieved 18 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199213276.001.0001/acprof-9780199213276.
Orangutans: Geographic Variation in Behavioral Ecology and Conservation. : Oxford University Press, 2008-12-11. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199213276.001.0001/acprof-9780199213276.
Wich SA, Utami Atmoko SS, Setia TM, van Schaik CP. Orangutans: Geographic Variation in Behavioral Ecology and Conservation. Oxford University Press; 2008. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199213276.001.0001/acprof-9780199213276. Accessed May 18, 2013.