^Communication With Extraterrestrial Intelligence(PDF). NSA. [2021-08-18]. （原始内容存档(PDF)于2021-07-09）. Sir Bernard Lovell, one of the world's leading radio astronomers, has calculated that, even allowing for a margin of error of 5000%, there must be in our own galaxy about 100 million stars which have planets of the right chemistry, dimensions, and temperature to support organic evolution.
^Peter Gersten, Frontiers of Science. What the U.S. Government Knows About UnidentifiedFlying Objects(PDF). NSA. [2021-08-18]. （原始内容存档(PDF)于2021-07-09）. New evidence for the existence of unconventional aerial objects relies no longer on the credibility of civilian reports but on the records of scientists, military personnel, intelligence analysts, law enforcement officers and other reliable and responsible people. Their testimony can be found in three thousand pages of previously classified documents on UFOs released (mostly through Freedom of Information Act suits) over the past few years by the Departments of State / Army / Navy /Air Force/Defense, the Federal Bureau of Investigation, the National Securitv Agency, the Detense Intelligence Agency and the central Intelligence Agency.
