Content Provider
DataCite Metadata Store (German National Library of Science and Technology)
309
North Dakota State University (NDSU): Digital Horizons
6
Biodiversity Heritage Library (BHL)
2
NOAA NCEI Environmental Data Archive (via DataONE)
2
The Online Books Page (Penn Libraries, University of Pennsylvania)
2
AAAS Resource Center (American Association for the Advancement of Science - via Crossref)
1
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe)
1
Cambridge University Press
1
Project Gutenberg (PG)
1
University of Calgary Journal Hosting
1
University of New England: DUNE (DigitalUNE)
1
Université de Nantes: HAL-UNIV-NANTES
1
Unknown
1