1. Catatonia and mania: patterns of cerebral dysfunction;Abrams;Biol. Psychiatry,1979
2. Negative vs positive schizophrenia. Definition and validation;Andreasen;Arch. Gen. Psychiatry,1982
3. Andreasen, N.C., 1984a. Scale for the assessment of negative symptoms (SANS), Iowa City, IA, University of Iowa.
4. Andreasen, N.C., 1984b. Scale for the assessment of positive symptoms (SAPS), Iowa City, IA, University of Iowa.
5. The distinction of positive and negative symptoms: the failure of a two-dimensional model;Ardnt;Br. J. Psychiatry,1991