1. NASA,"RoboticRefuelingMission,"URL:http://ssco.gsfc.nasa.gov/robotic_refueling_mission.html[citedAugust1,2015].
2. Butler,A."BigSavingsPromisedfromSbirsRedesign,Propulsion-PayloadDecoupling,"AviationWeek&SpaceTechnology, 24 June 2015, URL: http://aviationweek.com/space/big-savings-promised-sbirs-redesign-propulsion-payload-decoupling [cited 1 August 2015].
3. Harwood,W."STS-125MissionPreview:ABriefHistoryoftheHubbleSpaceTelescope,"9May2009,URL: http://www.cbsnews.com/network/news/space/125/125_HST_history.html[cited 1 August 2015].