https://en.wikipedia.org/wiki/Doping_in_the_United_Stateshttps://en.wikipedia.org/wiki/United_States_Anti-Doping_Agencyhttp://www.independent.co.uk/sport/general/athletics/world-athletics-2017-championships-usain-bolt-doping-sport-action-testing-a7873161.htmlhttp://www.adas.org.rs/en/vesti/2014/09/15/americki-sportisti-idu-na-doping-kontrolu-kao-svi-ostali/