1-http://www.ushistory.org/civ/
2-https://www.ancient.eu/
3-http://www.universityofcalicut.info/syl/BBACultureandCivilization.pdf
4-https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1850&context=ccr
5-https://www.britannica.com
Last modified: Monday, 17 December 2018, 1:39 PM