The Pentagon had a program to investigate UFOs, but it found no good evidence for aliens. What would prove the presence of extraterrestrials?
This is additional taxonomy that helps us with analytics
UFOs and the Boundaries of Science - Boston Review
Unidentified flying object - Wikipedia
Prepare for wave of extraterrestrial sightings in UK, say UFO experts, UFOs
10 places to see a UFO around the world – Lonely Planet - Lonely Planet
The moon is a long way off and it is impossible to get there - Science-Education-Research
[Graff, Garrett M.] on . *FREE* shipping on qualifying offers. UFO: The Inside Story of the US Government's Search for Alien Life
UFO: The Inside Story of the US Government's Search for Alien Life Here―and Out There
Analysis: Whistleblower testimonies did not change our basic understanding of UFOs
NASA's UFO Study Isn't Really Looking for Space Aliens
Interest in UFOs Is Not Just an American Phenomenon, Experts Say
The Science of Aliens, Part 6: Would They Be Religious?, Air & Space Magazine
UFO believers got one thing right. Here's what they get wrong
NASA Says UFO Sightings Are Not Extraterrestrial
Are We Alone?”: From Roswell to Oumuamua, Garrett Graff Traces the Long Hunt for Alien Life
Are Aliens Real?: How UFO Culture Took Over America