UFO researcher Leonard H. Stringfield was a prominent figure in the history of UFOlogy who investigated and published his research on the UFO crash retrievals. In his UFO Crash/Retrievals series, he published noted that during the Vietnam War, a US troop was sent to an area close to the Cambodia-North Vietnamese border where they engaged in combat with aliens.
In 1976, the Apollo 20 mission was launched, which included: William Rutledge, Aleksei Leonov, and Leona Snyder. They managed to land by the ship, get inside, inspect the interior of the ship, and the bodies of the pilots. One of the sources said that they not only examined the bodies but also took the head of one of the bodies with them.