Redalyc
Access 
Due to its many full texts and a rich in-content and metadata structure, Redalyc has became an important resource particularly for the Spanish-speaking scientific community across the world (also thanks to its Open Access policy).
Fee Policy 
Explicitly adhering to the Open Access policy, the portal content is open and free to the public, including full text downloading
Free Retrieved Material
With more than 10,000 articles available in pdf format, Redalyc is a crucial resource particularly for the Spanish-speaking scientific community across the world
Linking Richness
Along with a complex linking structure for internal browsing, there is a special page with some external links to similar resources