Content Provider
German Aerospace Center: elib - DLR electronic library
5
DataCite Metadata Store (German National Library of Science and Technology)
3
Media SuUB Bremen (Staats- und Universitätsbibliothek Bremen)
2
Directory of Open Access Journals: DOAJ Articles
1
Freie Universität Berlin: Refubium (FU Berlin)
1
Unknown
1