1. Department of Surgery OLVG West Amsterdam The Netherlands
2. Department of Epidemiology and Biostatistics, Amsterdam Public Health Research Institute VU University Medical Center Amsterdam The Netherlands
3. Centre for Surgical Research, School of Social and Community Medicine University of Bristol Bristol UK
4. Medical Library OLVG Amsterdam The Netherlands
5. Department of Bariatric and Upper GI Surgery Musgrove Park Hospital, Taunton and Somerset NHS Foundation Trust Taunton UK
6. Division of Surgery, Head and Neck University Hospitals Bristol National Health Service Foundation Trust Bristol UK
7. Section of Bariatric and Minimally Invasive Surgery Stanford University School of Medicine, Stanford University Stanford CA USA