1. Catholic University Leuven; Academic Centre for General Practice; Kapucijnenvoer 33 blok j - bus 7001 Leuven Belgium 3000
2. KU Leuven University; Social Research Methodology Group, Centre for Sociological Research, Faculty of Social Sciences; Parkstraat 45 Leuven Belgium BE 3000
3. CEBAM, Belgian Centre for Evidence-Based Medicine; Kapucijnenvoer 33, blok J, bus 7001 Leuven Vlaams-Brabant Belgium 3000