The truth is out there? Billy Meier's UFO images
Billy Meier is a Swiss national who in the 1970s claimed he had been in contact with aliens from the Pleiades star cluster - and had photographs to prove it.
Published in a 1979 book by former United States Air Force pilot Wendelle C Stevens, they later appeared in publicity material for US science-fiction programme The X-Files.
Now, they are up for auction at Sotheby's in the US, as part of a sale dedicated to space photography.
BBCEduard Albert "Billy" Meier claims he was first contacted by alien figures at the age of five, in 1942, and maintained regular contact throughout his life.
BBCThis series of images were taken in Switzerland in the spring of 1976.
BBCThis photo was used as the background of the "I want to believe" UFO poster that featured prominently in the office of FBI special agent Fox Mulder, played by David Duchovny, in The X-Files.
BBCInexpertly taken and faded, the images show blurry metallic blobs hovering or floating above the mountainous Swiss countryside.
BBCThough Stevens said the images had not been doctored, other ufologists are highly sceptical about the images.
BBCAll images copyright of Billy Meier, courtesy Sotheby's