1. https://www.faa.gov/about/office_org/headquarters_offices/ast/media/2016_Compendium.pdf
2. http://www.spiegel.de/wissenschaft/technik/alain-charmeau-die-amerikaner-wollen-europa-aus-dem-weltraum-kicken-a-1207322.html
3. https://fa.morganstanley.com/griffithwheelwrightgroup/mediahandler/media/106686/Space_%20Investment%20Implications%20of%20the%20Final%20Frontier.pdf
4. Davenport, Christian. The Space Barons; Elon Musk. Jeff Bezos, and the Quest to Colonize the Cosmos. PublicAffairs (2018). ISBN 978-1610398299
5. https://www.faa.gov/about/office_org/headquarters_offices/ast/media/2018_AST_Compendium.pdf