Futron Corporation. Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000 [online]. futron.com, [cit. 2020-02-11]. Dostupné online. Archivované 2011-07-11 z originálu.
Futron Corporation. Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000 [online]. futron.com, [cit. 2020-02-11]. Dostupné online. Archivované 2011-07-11 z originálu.