Spiegel, B., M. Camilleri, R. Bolus, V. Andresen, W.D. Chey, S. Fehnel, A. Mangel, N.J. Talley, and W.E. Whitehead. (2009). "Psychometric Evaluation of Patient-Reported Outcomes in Irritable Bowel Syndrome Randomized Controlled Trials: A Rome Foundation Report." Gastroenterology, 137(6):1944-1953.