Auditory hallucinations, source monitoring, and the belief that "voices" are real Michael Garrett, Raul Silva. Schizophrenia Bulletin. Washington: 2003. Tomo 29, No. 3; pág. 445

Global intellectual impairment does not accelerate with age in patients with schizophrenia: A cross-sectional analysis" Ron Hijman, Hilleke E Hulshoff Pol, Margriet M Sitskoorn, Rene S Kahn. Schizophrenia Bulletin. Washington: 2003. Tomo 29, No. 3; pág. 509