Pirolli, Peter. "Future Directions: Upward, Downward, Inward, and Outward." Information Foraging Theory: Adaptive Interaction with Information. : Oxford University Press, 2007-05-03. Oxford Scholarship Online. 2010-04-01. Date Accessed 20 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195173321.001.0001/acprof-9780195173321-chapter-10>.
Pirolli, P.(2007-05-03). Future Directions: Upward, Downward, Inward, and Outward. In Information Foraging Theory: Adaptive Interaction with Information. : Oxford University Press. Retrieved 20 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195173321.001.0001/acprof-9780195173321-chapter-10.
Pirolli, Peter. "Future Directions: Upward, Downward, Inward, and Outward." In Information Foraging Theory: Adaptive Interaction with Information. : Oxford University Press, 2007-05-03. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195173321.001.0001/acprof-9780195173321-chapter-10.
Pirolli P. Future Directions: Upward, Downward, Inward, and Outward. In: Pirolli PLT. Information Foraging Theory: Adaptive Interaction with Information. Oxford University Press; 2007. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195173321.001.0001/acprof-9780195173321-chapter-10. Accessed May 20, 2013.