Ackerman SJ, Mordin M, Reblando J, Xu X, Schein J, Vallow S, Brennan M. Patient-reported utilization patterns of fentanyl transdermal system and oxycodone hydrochloride controlled-release among patients with chronic nonmalignant pain. J Manag Care Pharm. 2003 May 1;9(3):223-31.