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.
Hauber B, Candrilli S, Snyder EH, McBurney CR. Validation of a model to assess long-term disease progression in Alzheimer's disease patients treated with rivastigmine. Neurobiol Aging. 2004 Jan 1;25:S136.