The UFO Encyclopedia is a highly acclaimed, authoritative source that offers extensive coverage of the UFO phenomenon. This new fourth edition, authored again by one of the world's foremost authority on UFOs—Jerome Clarke—includes over a hundred new entries and offers context for the reams of declassifed UFO-related documents that have been released in the United States, Brazil, and other countries. The UFO Encyclopedia explores secret government programs that were revealed in recent years and before; and compiles and explains the UFO phenomena in all its aspects—the sightings, close encounters, investigations, debates, symposia, personalities, hoaxes, debunking campaigns, and conspiracy theories—including expert analysis of the UFO era and historical context for sightings in the century and a half before the UFO era.