1. Academic Search Premier (EBSCO)
2. MathSciNet (AMS)
3. IEEE Xplore
4. ScienceDirect - Sciverse (Elsevier)
5. ACM Digital Library
6. Dialnet (La Rioja University)
7. IOP Science Extra
8. Nature
9. SIAM
10. Springer
11. AAAS Science
12. Zentralblatt MATH
13. CERN Document Server
14. ICYT - Ciencia y Tecnología
15. ISI Web of Knowledge
16. INSPEC (Thomsom Scientific)
17. SCIRUS (Elsevier)
18. SSRN (Social Science Research Network)