1. American Psychiatric Association (1987) Diagnostic and statistical manual of mental disorders (3rd edition-revised). American Psychiatric Press, Washington
2. Andreasen NC (1983) The scale for the assessment of negative symptoms. University of Iowa, Iowa City
3. Andreasen NC (1984) The scale for the assessment of positive symptoms. University of Iowa, Iowa City
4. Andreasen NC, Olsen S (1982) Negative vs. positive schizophrenia. Arch Gen Psychiatry 39:789–794
5. Arbeitsgemeinschaft für Methodik und Dokumentation in der Psychiatrie (1981) Das AMDP-System. Manual zur Dokumentation psychiatrischer Befunde. Springer, Berlin Heidelberg New York