Sometimes it is useful to have some non-Google search sites. Especially when it comes to academic topics. Here's a few:

RefSeek

Academic Resource Search. More than a billion sources: encyclopedia, monographies, magazines.

WorldCat

A search for the contents of 20 thousand worldwide libraries. Find out where lies the nearest rare book you need. (JavaScript required.)

Springer Link

Access to more than 10 million scientific documents: books, articles, research protocols.

Bioline International

Is a library of scientific bioscience journals published in developing countries.

RePEc

Volunteers from 102 countries have collected almost 4 million publications on economics and related science.

Science.gov

is an American state search engine on 2200+ scientific sites. More than 200 million articles are indexed.

PDF Drive

Is the largest website for free download of books in PDF format. Claiming over 225 million names.

Bielefeld Academic Search Engine

Is one of the most powerful researches on academic studies texts. More than 100 million scientific documents, 70% of them are free

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