Content Provider
LeibnizOpen (The Leibniz Association)
18
Unknown
4
Copernicus Publications: E-Journals
2
DataCite Metadata Store (German National Library of Science and Technology)
2
Directory of Open Access Journals: DOAJ Articles
2
Niedersächsisches Online-Archiv NOA
2
ETH ZĂĽrich Research Collection
1
University of California: eScholarship
1