Based on the conference abstract: The aim of the study is to determine if there is a difference in the yield of PubMed and OVID MEDLINE and to identify which has the highest yield. The researcher selected ten reviews by the Back, Palliative Care, and Supportive Care (PaPaS) Cochrane Review Group and then ascertained how many of the included studies were contained in PubMed and OVID Medline. In the 5 physical interventions reviews, PubMed contained 57% (43/76) and OVID MEDLINE 49% (37/76). The results of the other 5 reviews are not presented in the abstract. The author explain the higher number of references retrieved in PubMed was due to  the fact that PubMed indexes citations from journals that precede the date those same journals are selected for Ovid indexing.