1. Imperial College London; Department of Primary Care and Public Health, Faculty of Medicine; The Reynolds Building, Charing Cross Campus St. Dunstan's Road London UK W6 8RP
2. University of Alberta; Department of Emergency Medicine; Room 1G1.43 Walter C. Mackenzie Health Sciences Centre 8440 112th Street Edmonton AB Canada T6G 2B7
3. University of Alberta; School of Public Heath; Edmonton Canada
4. St George's, University of London; Population Health Research Institute; Cranmer Terrace Tooting London UK SW17 0RE