1. The Space Report 2013, Space Foundation, Colorado Springs, CO (2013).
2. Result calculated from published data: SATELLITES TO BE BUILT & LAUNCHED BY 2022, WORLD MARKET SURVEY, Forecasts to 2022, 2013 Brochure, Euroconsult (2013).
3. SATELLITES TO BE BUILT & LAUNCHED BY 2022, WORLD MARKET SURVEY, Forecasts to 2022, 2013 Brochure, Euroconsult (2013).
4. Analysis of the Iridium 33-Cosmos 2251 Collision;Kelso,2009
5. Yan peipei, Liu Kai, Duan Jing, et.al. Switch-zoom optical system design of large aperture ground-based photoelectric detection.