http://hiru.mcmaster.ca/hiru/HIRU_Hedges_home.aspx

The focus of the Hedges Project, which is funded by the National Library of Medicine, is to investigate ways to develop and harness search filters ("hedges") that will improve retrieval of scientifically sound and clinically relevant study reports from large, general purpose, biomedical research bibliographic databases including MEDLINE, EMBASE, and PsycINFO.