Content Provider
Directory of Open Access Journals: DOAJ Articles
4
DataCite Metadata Store (German National Library of Science and Technology)
2
CyberLeninka (Scientific Electronic Library)
1
HELDA – University of Helsinki Open Repository
1
International Scientific Publications
1
MDPI Open Access Publishing
1
SAGE Publications (via Crossref)
1
Tomsk Polytechnic University (TPU): Electronic Archive
1