The Open DOI resolver searches multiple repositories.
OpenDOAR Searches content in repositories worldwide.
OpenAIRE Searches content held in European repositories.
PubMed Central(PMC) a free archive of biomedical and life sciences journal literature, from the National Library of Medicine.
OAIster A collaboration between the University of Michigan and OCLC. A union catalog of millions of records representing open access resources that was built by harvesting from open access collections worldwide using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH).
Digital Commons Network Search across repositories hosted on this Bepress platform. Includes CUNY's Academic Works.