Useful Websites
If you are in need of a particular e-book, you can download it for free from the links below
http://lib.freescienceengineering.org
https://www.englishforums.com/
https://owl.english.purdue.edu/sitemap/
http://www.ldoceonline.com
http://books.google.com/ngrams
http://www.gresham.ac.uk