The Centre for Science and Technology Studies (CWTS), Leiden University was commissioned by HEFCE to assess the potential usefulness of citation databases other than Thompson Reuters' Web of Science (WoS) for use in the REF. The study focuses on Scopus, published by Elsevier and on ISI Proceedings, published by Thomson Reuters.
CWTS found that, in general, Scopus covers much of the same material as the WoS and ISI Proceedings and in some areas provides a higher level of coverage. However WoS is in the process of increasing its coverage. There are also some important differences in the data structure. Overall, the report found that Scopus should be considered as a potential alternative to the WoS for the purposes of the REF.