1. Department of Orofacial Pain and Dysfunction Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and Vrije Universiteit Amsterdam Amsterdam The Netherlands
2. Medical Library Vrije Universiteit Amsterdam Amsterdam The Netherlands
3. Department of Public Health and Primary care Leiden University Medical Centre Leiden The Netherlands
4. Physiological Psychology Otto Friedrich University Bamberg Bamberg Germany
5. Marie Curie Palliative Care Research Department Division of Psychiatry University College London London UK