Content Provider
LeibnizOpen (The Leibniz Association)
37
Defense Technical Information Center: DTIC Technical Reports database
18
DataCite Metadata Store (German National Library of Science and Technology)
13
Ohio State University (OSU): Knowledge Bank
12
Unknown
8
Zenodo
5
Directory of Open Access Journals: DOAJ Articles
3
Claremont Colleges Digital Library (CCDL)
2
Georgia Institute of Technology: SMARTech - Scholarly Materials and Research at Georgia Tech
2
Renate - Repositorium für Naturwissenschaften und Technik (TIB Hannover)
2
The Library of Congress: American Memory
2
ePLUS - Open Access Publikationsserver der Universität Salzburg
2
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe)
1
Biblioteca Digital FCEN-UBA (Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires)
1
Digital Repository of Scientific Institutes (RCIN)
1
GettDigital (Gettysburg College Digital Collections)
1
Harvard University: Harvard Collections
1
Jagiellonian University Repository
1
National Cheng Kung University: NCKU Institutional Repository
1
Open Research Library
1
Project Gutenberg (PG)
1
SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy)
1
Texas Tech University: TTU DSpace Repository
1
The University of Arizona: UA Campus Repository
1
Treasures @ UT Dallas
1
USRA Houston Repository (Universities Space Research Association)
1
University of Calgary Journal Hosting
1
University of Michigan: Deep Blue
1
Université de Nantes: HAL-UNIV-NANTES
1
Washington State University: WSU Libraries Digital Collections
1