Candrilli SD, Davis KL, Iyer S. Impact of constipation on opioid use patterns, health care resource utilization, and costs in cancer patients on opioid therapy. J Pain Palliat Care Pharmacother. 2009 Sep 1;23(3):231-41.
Watson V, Ryan M. Exploring preference anomalies in double bounded contingent valuation. J Health Econ. 2007 May 1;26(3):463-82. doi: 10.1016/j.jhealeco.2006.10.009
Lovas K, Geher P, Whalley D, McKenna S, Meads D, Kalo Z. Hungarian adaptation of a disease-specific quality-of-life questionnaire in patients with ankylosing spondylitis. Orv Hetil. 2002 Aug 11;43(32):1893-7.