1. Theory in practice: Increasing professional effectiveness;Argyris,1974
2. De publieke opinie ondervraagd: Over de zin en onzin van opiniepeilingen. [Examining public opinion: About the sense and nonsense of opinion polls];Billiet,2000
3. Unpublished data from ISPO 2003 data wave (variable Q61_D);Billiet,2005
4. Kwaliteit in de overheid [Quality in public administration];Bouckaert,2003
5. Kwaliteit in de overheid [Quality in public administration];Bouckaert,1999