http://www.history.com/topics
https://www.pbslearningmedia.org/
http://www.discoveryeducation.com
http://www.biography.com
http://www.time.com
http://big6.com
http://prezi.com/prezi-for-education/
http://www.sonofacitation.com
http://www.barnesandnoble.com/
http://www.booksamillion.com/
http://owl.english.purdue.com/
http://grammarbook.com/