Luciano JV, Barrada JR, Aguado J, Osma J, García-Campayo J. Bifactor analysis and construct validity of the HADS: a cross-sectional and longitudinal study in fibromyalgia patients. Psychological Assessment. 2014 Jun;26(2):395-406.
Bray JW, Davis KL, Graver L, Schroeder D, Buck JA, Dilonardo J, Vandivort R. Mental health and substance abuse treatment utilization among individuals served by multiple public agencies in 3 states. J Behav Health Serv Res. 2005 Jan 1;32(3):282-93.