US debt default

http://www.ehd.org/science_technology_largenumbers.php
https://www.marketwatch.com/story/heres-how-the-us-got-to-20-trillion-in-debt-2017-03-30
http://www.polidiotic.com/by-the-numbers/us-national-debt-by-year/
http://www.businessinsider.com/graph-worlds-debt-share-by-country-2015-8
http://www.bbc.com/news/business-24453400
https://www.theatlantic.com/international/archive/2016/09/cost-wars-iraq-afghanistan/499007/
https://www.nbcnews.com/businessmain/whats-worst-could-happen-7-debt-default-doomsday-scenarios-8C11366851
http://money.cnn.com/2016/05/10/news/economy/us-debt-ownership/index.html
https://www.theguardian.com/world/2017/jul/30/greek-debt-crisis-people-cant-see-any-light-at-the-end-of-any-tunnel
https://www.forbes.com/sites/johntharvey/2012/09/10/impossible-to-default/#33555e4c1180