Content Provider
Hathi Trust Digital Library
142
DataCite Metadata Store (German National Library of Science and Technology)
131
Biodiversity Heritage Library (BHL)
126
Unknown
120
Directory of Open Access Journals: DOAJ Articles
88
Cambridge University Press
78
University of Calgary Journal Hosting
78
NOAA NCEI Environmental Data Archive (via DataONE)
47
David Rumsey Historical Map Collection (Cartography Associates)
41
The Seattle Public Library Special Collections Online
37
Defense Technical Information Center: DTIC Technical Reports database
35
University of Washington, Seattle: Digital Collections
34
DataCite
30
University of Michigan: Digital Collections
29
RePEc (Research Papers in Economics)
26
The Online Books Page (Penn Libraries, University of Pennsylvania)
24
University of Wisconsin, Milwaukee: UWM Libraries Digital Collections
22
Arctic Institute of North America
21
Informa
21
Université Laval: CorpusUL
21
Copernicus Publications: E-Journals
18
Arctic Data Center (via DataONE)
17
Charles University CU Digital repository
17
Informa (via Crossref)
17
Zenodo
17
Springer Nature (via Crossref)
15
University of Toronto Press (U Toronto Press - via Crossref)
15
Brill
14
North Dakota State University (NDSU): Digital Horizons
14
Project Gutenberg (PG)
13
Wiley Online Library
13
Bavarian Digital Repository (BDR - Bayerische Staatsbibliothek Munich, BSB)
12
DR-NTU (Digital Repository at Nanyang Technological University, Singapore)
12
Harvard University: Harvard Collections
12
MacEwan Open Journals (MacEwan University)
12
ScienceDirect (Elsevier - via Crossref)
12
uO Research (University of Ottawa - uOttawa)
12
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe)
11
JSTOR (via Crossref)
11
Oxford University Press (via Crossref)
11
De Gruyter
10
PubMed Central (PMC)
10
University of Miami: Digital Collections
10
Creighton University: Creighton Digital Repository (CDR)
9
Naval Postgraduate School: Calhoun
9
Niedersächsisches Online-Archiv NOA
9
OpenEdition
9
PANGAEA - Data Publisher for Earth & Environmental Science
9
SAGE Publications
9
Theses Canada/Thèses Canada (Library and Archives Canada)
9
more ...