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https://www.nasa.gov/sites/default/files/files/SP-2014-617.pdf
3. NASA, The Vision for Space Exploration (2004). Retrieved from
https://history.nasa.gov/Vision_For_Space_Exploration.pdf
4. D. Mosher, Russia is Squeezing NASA for More than $3.3 billion—And There’s Little Anyone Can Do About It (2016). Retrieved from Business Insider:
http://www.businessinsider.de/astronaut-cost-per-soyuz-seat-2016-9?r=U.S.&IR=T
5. S.3729—111th Congress, National Aeronautics and Space Administration Authorization Act of 2010 (2009–2010). Retrieved from Congress.Gov:
https://www.congress.gov/bill/111th-congress/senate-bill/3729