1. Department of Internal Medicine; University of Groningen; University Medical Centre Groningen
2. Department of Internal Medicine; Medical Centre Leeuwarden
3. Department of Internal Medicine; Onze Lieve Vrouwe Gasthuis; Amsterdam
4. Department of Internal Medicine; Het Diakonessenhuis; Meppel
5. Department of Internal Medicine; Sint Franciscus Gasthuis Rotterdam; The Netherlands