General:
http://www.nydailynews.com/news/top-10-richest-people-time-gallery-1.1186737?pmSlide=1.1186726
https://www.cheatsheet.com/money-career/the-10-richest-people-of-all-time.html/?a=viewall
https://www.celebritynetworth.com/articles/entertainment-articles/25-richest-people-lived-inflation-adjusted/
http://www.neatorama.com/2008/07/09/10-richest-people-of-all-time-and-how-they-made-their-fortunes/
https://www.therichest.com/celebnetworth/politician/royal/nikolai-alexandrovich-romanov-net-worth/

Cornelius Vanderbilt:
http://www.history.com/topics/cornelius-vanderbilt
Henry Ford:
https://www.thehenryford.org/explore/stories-of-innovation/visionaries/henry-ford/
Muammar Gaddafi:
http://www.bbc.com/news/world-africa-12688033
https://www.theguardian.com/world/2011/oct/20/muammar-gaddafi-timeline
Jakob Fugger:
https://nypost.com/2015/07/26/meet-historys-richest-man-who-changed-christianity/

William the Conqueror:
http://www.bbc.co.uk/timelines/zp88wmn
Mir Osman Ali Khan
http://www.southreport.com/25-facts-might-not-known-last-nizam-hyderabad/

Tzar Nicholas II:
https://www.rbth.com/multimedia/pictures/2016/10/06/alexandra-fyodorovna-romanova_636461
Andrew Carnegie:
https://www.biography.com/people/andrew-carnegie-9238756
John D. Rockefeller:
https://www.smithsonianmag.com/smart-news/john-d-rockefeller-richest-person-ever-live-period-180961705/
http://www.history.com/topics/john-d-rockefeller

Mansa Musa:
https://www.cnbc.com/2015/07/31/richest-man-of-all-time-try-king-of-timbuktu.html
http://www.businessinsider.com/mansa-musa-the-richest-person-in-history-2016-2