SHERPA/RoMEOSHERPA/RoMEO began as a UK research project developed at the University of Loughborough and is now maintained by the Centre for Research Communications (CRC) at the University of Nottingham. It’s an excellent starting point to find summaries of “permissions that are normally given as part of each publisher’s copyright transfer agreement.” Policies can be searched for by journal titles or their ISSNs or by a publisher’s name.