Internet Search Engines

refseek.com A search engine for academic resources. Over a billion sources
worldcat.org Search in the contents of 20,000 world libraries
link.springer.com Access to over 10 million scientific documents: books, articles
bioline.org.br A library of published biological science journals
repec.org Volunteers from 102 countries collected almost 4 million contributions
science.gov A U.S. government search engine for over 2200 scientific websites
pdfdrive.com The largest free PDF book download website. Claim more than 225 million titles
base-search.net One of the most powerful search engines for academic research texts. Over 100 million scientific articles, 70% of which are free
primo.nlr.ru Rare archived books/codexs (Russian)
loc.gov Over 100 thousand documents, texts, books, PDFs, codex's, etc
history-fiction.ru Rare historical literatures
academia.edu Historical literature and text
holybooks.com The largest collection of high-quality sacred texts, holy books, spiritual texts as PDF ebooks
lexicity.com A comprehensive index for ancient language resources
eudocs.lib.byu.edu European History