there are still a large number of excellent research engines in the world that specialize in books, science, and other smart information.Keep a list of sites you’ve never heard of.

www.refseek.com is an academic resource search engine. More than a billion sources

www.worldcat.org – search within 20,000 global libraries.

https://link.springer.com – access to more than 10 million scientific documents: books, articles,

www.bioline.org.br is a library of published bioscience magazines

http://repec.org – Volunteers from 102 countries collected nearly 4 million publications

www.science.gov is a U.S. government search engine for more than 2200 scientific sites.

www.pdfdrive.com is the largest website to download free PDF books. Claim 225 million+ titles.

www.base-search.net is one of the most powerful research engines for academic research texts. More than 100 million scientific articles 70% free