@book{circref2460, title = {Undertaking systematic reviews of research on effectiveness : CRD’s guidance for those carrying out or commissioning reviews}, booktitle = {Series: CRD report ; 4}, author = {NHS Centre for Reviews and Dissemination.}, publisher = {Centre for Reviews and Dissemination, University of York}, year = {2001}, address = {York, England}, url = {}, keywords = {Health Care, Health Services Research, Quality Assurance} }