Systems for grading the quality of evidence and the strength of recommendations I: Critical appraisal of existing approaches The GRADE Working Group

David Atkins, Martin P. Eccles, Signe Flottorp, Gordon H Guyatt, David Henry, Suzanne Hill, Alessandro Liberati, Dianne O'Connell, Andrew D. Oxman, Bob Phillips, Holger J. Schünemann, Tessa Tan Torres Edejer, Gunn E. Vist, John W. Williams