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web.archive.org
Report of the Task Force on potentially hazardous Near Earth Objects, p49, Department of Trade and Industry (UK), September 2000, Pub 4990/5k/9/00/NP.URN00/1041, retrieved online보관됨 7 3월 2009 - 웨이백 머신, 16 May 2009.
"Near Earth Object Program", National Aeronautics and Space Administration, retrieved onlineArchived 2013년 2월 2일 - 웨이백 머신 3 May 2009.