1. Department of Internal Medicine, Northwest Clinics, Alkmaar, The Netherlands
2. Amsterdam Rheumatology and Immunology Centre, Amsterdam, The Netherlands
3. Department of Nephrology, VU University Medical Centre, Amsterdam, The Netherlands
4. Medical Library, Vrije Universiteit, Amsterdam, The Netherlands
5. Department of Epidemiology & Biostatistics, VU University Medical Centre, Amsterdam, The Netherlands