Peter Davenport has received more phone calls than he cares to count that have an unusual opening: "Please believe me, I'm not crazy."

For Davenport, director of the National UFO Reporting Center in Seattle, it's part of the job.

Davenport spoke Sunday at the Little Green Men Festival in Hopkinsville with tales of what he believes are some of the more fascinating, provable cases reported. The festival, at the Hopkinsville-Christian County Conference and Convention Center, commemorates the 50th anniversary of the Aug. 21, 1955, report of an alien invasion at Kelly.

After a lifetime of studying what many brush off as science fiction, Davenport is feels certain that UFOs exist and have been witnessed on Earth, and second, that the government has known about them for decades.