„Becoming a Multiplanet Species”(PDF). 68th annual meeting of the International Astronautical Congress in Adelaide, Australia: SpaceX. . Arhivat din original(PDF) la . Accesat în .
„Becoming a Multiplanet Species”(PDF). 68th annual meeting of the International Astronautical Congress in Adelaide, Australia: SpaceX. . Arhivat din original(PDF) la . Accesat în .