Content Provider
APS Digital Library (American Philosophical Society)
135
DataCite Metadata Store (German National Library of Science and Technology)
112
Unknown
46
University of Alaska: ScholarWorks@UA
45
Wiley Online Library (via Crossref)
26
Hathi Trust Digital Library
25
University of British Columbia: cIRcle - UBC's Information Repository
25
Wiley Online Library
22
OLAC: Open Language Archives Community
21
Directory of Open Access Journals: DOAJ Articles
17
University of Chicago Press (via Crossref)
14
University of Calgary Journal Hosting
13
Arca (BC's Digital Treasures)
12
Universitat de Girona: DUGi Fons Especials (UdG Digital Repository)
12
Cambridge University Press
11
HighWire Press (Stanford University)
10
Informa (via Crossref)
10
Oklahoma State University: Digital Collections @ OKSTATE Library
9
Open Access Journal Hosting (University of British Columbia)
9
Springer Nature (via Crossref)
8
University of California: eScholarship
8
University of Northern Colorado: Digital UNC
8
Biodiversity Heritage Library (BHL)
7
Digital Collections of Colorado (Colorado State University)
7
Duke University Press
7
Johns Hopkins University Press (via Crossref)
7
Mountain Scholar (Digital Collections of Colorado and Wyoming)
7
Theses Canada/Thèses Canada (Library and Archives Canada)
7
University of Michigan: Digital Collections
7
SAGE Publications (via Crossref)
6
WikiBooks - Open-content textbooks
6
Érudit.org (Université Montréal)
6
Cambridge University Press (via Crossref)
5
Informa
5
Johns Hopkins University Press
4
Oxford University Press
4
Oxford University Press (via Crossref)
4
PubMed Central (PMC)
4
SAGE Publications
4
ScholarSpace at University of Hawaii at Manoa
4
University of California Press (via Crossref)
4
University of Chicago Press
4
University of Wisconsin Press (UW Press - via Crossref)
4
American Museum of Natural History: AMNH scientific publications
3
Brigham Young University (BYU): Digital Collections
3
JSTOR (via Crossref)
3
MDPI Open Access Publishing
3
Max Planck Society: MPG.PuRe
3
PRISM - University of Calgary Digital Repository
3
Princeton Theological Seminary: Theological Commons
3
more ...