Pitts-Singer, Theresa L. "Past and Present Management of Alfalfa Bees." Bee Pollination in Agricultural Ecosystems. : Oxford University Press, 2008-07-31. Oxford Scholarship Online. 2008-09-01. Date Accessed 19 Jun. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195316957.001.0001/acprof-9780195316957-chapter-7>.
Pitts-Singer, T.(2008-07-31). Past and Present Management of Alfalfa Bees. In Bee Pollination in Agricultural Ecosystems. : Oxford University Press. Retrieved 19 Jun. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195316957.001.0001/acprof-9780195316957-chapter-7.
Pitts-Singer, Theresa L. "Past and Present Management of Alfalfa Bees." In Bee Pollination in Agricultural Ecosystems. : Oxford University Press, 2008-07-31. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195316957.001.0001/acprof-9780195316957-chapter-7.
Pitts-Singer TL. Past and Present Management of Alfalfa Bees. In: James R, Pitts-Singer TL. Bee Pollination in Agricultural Ecosystems. Oxford University Press; 2008. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195316957.001.0001/acprof-9780195316957-chapter-7. Accessed June 19, 2013.