E -books & Journals
Religious E-books
Books for the Visually Impaired
E-Journals
ScienceOpen
CORE
Education Resources Information Center
arXiv e-Print Archive
Social Science Research Network
Public Library of Science
OpenDOAR
Bielefeld Academic Search Engine
Digital Library of the Commons Repository
Paperity
dblp Computer Science Bibliography
BioMed Central
JURN
Dryad
EThOS
PubMed
Zenodo
Semantic Scholar