Keep a list of sites you never heard of!
- [RefSeek](http://www.refseek.com) - Academic Resource Search. More than a billion sources: encyclopedia, monographies, magazines.
- [WorldCat](http://www.worldcat.org) - A search for the contents of 20 thousand worldwide libraries. Find out where lies the nearest rare book you need.
- [Springer Link](https://link.springer.com) - Access to more than 10 million scientific documents: books, articles, research protocols.
- [Bioline](http://www.bioline.org.br) - A library of scientific bioscience journals published in developing countries.
- [RePEc](http://repec.org) - Volunteers from 102 countries have collected almost 4 million publications on economics and related science.
- [Science.gov](http://www.science.gov) - An American state search engine on 2200+ scientific sites. More than 200 million articles are indexed.
- [BASE](http://www.base-search.net) - One of the most powerful searches on academic studies texts. More than 100 million scientific documents, 70% of them are free.