1. University of Oxford; Nuffield Department of Primary Care Health Sciences; Radcliffe Observatory Quarter Woodstock Road Oxford Oxfordshire UK OX2 6GG
2. University of Vermont; Departments of Psychological Sciences & Psychiatry; 1 S Prospect Street, Mail Stop 482, OH4 Burlington VT USA 05405
3. Birmingham Dental Hospital; Oral Surgery Department; 5 Mill Pool Way Birmingham UK B5 7EG