1. Hôpital St-François-D'Assise; Centre de recherche CHUQ; 10, de l'Espinay Local D1-724D Quebec City Quebec Canada G1L 3L5
2. The Cochrane Collaboration; Cochrane Editorial Unit; 11-13 Cavendish Square London UK W1G 0AN
3. University of Alberta; Department of Emergency Medicine; Room 1G1.43 Walter C. Mackenzie Health Sciences Centre 8440 112th Street Edmonton Alberta Canada T6G 2B7
4. University of Alberta; School of Public Heath; Edmonton Canada