1. AGI-Lockheed Tout Commmercial Space Surveillance Systems,
http://spacenews.com/41727agi-lockheed-tout-commercial-space-surveillance-systems/#sthash.5CzBha2C.dpuf
. Last Accessed 16 Jan 2016
2. M. Cooney, 10 crucial issues around controlling orbital debris, directing space traffic. Network World, 12 May 2014,
http://www.networkworld.com/article/2226898/security/10-crucial-issues-around-controlling-orbital-debris-directing-space-traffic.html
. Last Accessed 16 Jan 2016
3. Goddard NASA Team,
http://www.nasa.gov/content/goddard/nasa-team-proposes-to-use-laser-to-track-orbital-debris/Last
. Accessed 16 Jan 2016
4. L. Martin, Lands $914 Million Space Fence Contract (2014),
http://spacenews.com/40776lockheed-martin-lands-914m-space-fence-contract/
. Last Accessed 16 Jan 2016
5. J.N. Pelton, New Solutions to Orbital Debris Problems (Springer Press, New York, 2015)