1. GAO-21-306 Assessments of Major NASA Projects (U.S. Government Accountability Office, Washington, 2021).
2. GAO-21-520T Space Acquisitions (U.S. Government Accountability Office, Washington, 2021).
3. GAO-21-330 NASA Lunar Programs (U.S. Government Accountability Office, Washington, 2021).
4. Measurement of returns to scale using a non-radial DEA model
5. “Studies concerning space debris, the safe use of space objects with nuclear energy sources on board and the problems of their collisions with space debris,” 58Th session, A/AC.105/C.1/118/Add.1 (UN Committee on the Peaceful Uses of Outer Space, Vienna, 1–12 February 2021).