Institutional Repositories World

1

Arxiv.org e-Print Archive

http://arxiv.org/ 

2

Social Science Research Network

https://ssm.com/en/index.cfm

3

Smithsonian/NASA Astrophysics Data System

http://adsabs.harvard.edu/ 

4

Research Papers in Economics

http://repec.org/

5

CiteSeerX

http://citeseerx.ist.psu.edu/index

6

University of Callifornia eScholarship Repository

https://escholarship.org/