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.
Caro JJ, Ward A, Craig T, Huybrecht K, Arana A, Wait S, Eleftheriou A. Impact of thalassemia major on patients and their families. Acta Haematol. 2002;107(3):150-7.