Grading quality of evidence and strength of recommendations - Atkins, D; Best, D; Briss, P A; Eccles, M; Falck-Ytter, Y; Flottorp, S; Guyatt, G H; Harbour, R T; Haugh, M C; Henry, D; Hill, S; Jaeschke, R; Leng, G; Liberati, A; Magrini, N; Mason, J; Middleton, P; Mrukowicz, J; O’Connell, D; Oxman, A D; Phillips, B; Schünemann, H J; Edejer, T; Varonen, H; Vist, G E; Williams, J W, Jr.; Zaza, S (BMJ, 2004)