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.
Price C, Golden B, Harrington M, Konewko R, Wasil E, Herring W. Reducing boarding in a post-anesthesia care unit. Prod Oper Manag. 2011 May 1;20(3):431-41.