"Sentry Risk Table". Wayback Machine: NASA/JPL Near-Earth Object Program Office. 15 August 2013. Archived from the original on 25 November 2013. Retrieved 15 August 2013.
"Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 23 January 2014.
"Sentry Risk Table". Wayback Machine: NASA/JPL Near-Earth Object Program Office. 15 August 2013. Archived from the original on 25 November 2013. Retrieved 15 August 2013.
"Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 23 January 2014.