Marx J, Hockberger R, and Walls R. 2014. Abdominal Pain in Rosen's emergency medicine [8th ed.], 27, 22-231.e1. Philadelphia: Elsevier Saunders.
Schiller L. Abdominal pain syndrome. http://www.acg.gi.org/patients/gihealth/aps.asp. 2013. Accessed October 29, 2014.