Bjornsdottir E, Janson C, Lindberg E, Arnardottir ES, Benediktsdottir B, Garcia-Aymerich J, Carsin AE, Real FG, Toren K, Heinrich J, Nowak D, Sanchez-Ramos JL, Demoly P, Arenas SD, Navarro RC, Schlunssen V, Raherison C, Jarvis DL, Gislason T. Respiratory symptoms are more common among short sleepers independent of obesity. BMJ Open Respir Res. 2017 Aug 30;4(1):e000206. doi: 10.1136/bmjresp-2017-000206
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.