OCEBM Levels of Evidence Working Group = Jeremy Howick ICJLL, Paul Glasziou, Trish Greenhalgh, Carl Heneghan, Alessandro Liberati, Ivan Moschetti, Bob Phillips, Hazel Thornton, Olive Goddard and Mary Hodgkinson (2011)
OCEBM Levels of Evidence Working Group*. “The Oxford Levels of Evidence 2”.