Aguado J, Campbell A, Ascaso C, Navarro P, Garcia-Esteve L, Luciano JV. Examining the factor structure and discriminant validity of the 12-Item General Health Questionnaire (GHQ-12) among Spanish postpartum women. Assessment. 2012 Dec 19;19(4):517-25.
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.