S. Gupta, MS, H. Patel, PharmD, J. Scopel, MD, MBA, and R. R. Mody, MBA, PhD, “Impact of constipation on opioid therapy management among long-term opioid users, based on a patient survey”, J of Opioid Management, vol. 11, no. 4, pp. 325–338, Jul. 2015.