Complex sentence: The two Air Force reports on the Roswell UFO incident, published in 1994/5 and 1997, form the basis for much of the skeptical explanation for the 1947 incident, the purported recovery of aliens and their craft from the vicinity of Roswell, New Mexico.
Split into simpler sentences: The two Air Force reports on the Roswell UFO incident published in 1994/5 and 1997 form the basis for much of the skeptical explanation for the 1947 incident. The Roswell UFO incident was the purported recovery of aliens and their craft from the vicinity of Roswell, New Mexico.