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.
Freund DA, Hurley RE, Adamache KW, Mauskopf J. The performance of urban and public hospitals and NHCs (neighborhood health centers) under Medicaid capitation programs. Hosp Health Serv Adm. 1990 Jan 1;35(4):525-46.