1. Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets;Lewis,1997
2. For detailed discussion on the increased awareness of this area in the early years of the 21st Century See Mark Williamson, Space: the Fragile Frontier, American Institute of Aeronautics and Astronautics,2006
3. Protecting our space interests;Brachet;ROOM Space J. Wint.,2017
4. Assessment of the consequences of the Fengyun-1C breakup in low earth orbit;Pardini;Adv. Space Res.,2009
5. https://swfound.org/media/6575/swf_iridium_cosmos_collision_fact_sheet_updated_2012.pdf. (Accessed 12 February 2017).