1. Department of Medical and Health Sciences, Division of Community Medicine, Linköping University, Linköping, Sweden;
2. HELIX Competence Centre, Linköping University, Linköping, Sweden;
3. School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria, Republic of South Africa;
4. Dalla Lana School of Public Health, University of Toronto, Toronto, Canada;
5. Canadian Memorial Chiropractic College, Toronto, Canada