(Reference: Loren Gross, UFO's: A History 1952: August, page 48.)
Loren Gross wrote:
One of the hardest kinds of cases to explain in mundane terms is a radar-visual incident. On August 18th there seems to have been one at Duncanville, Texas Air Force records say this about the eyewitnesses' account: "Visual sightings were made at 0245 on 18 August 52 of a slow moving object and reported to Carswell AFB. Red and Green lights changing to white were noted. Object moved up and down, hovered and then moved off at a rapid rate of speed." 187.
The radar contact is mentioned this way:
"At 0247 Z two unidentified aerial objects picked up by the 147 AC&W Squadron, Duncanville, Texas. Objects changed directions several times and had an estimated speed of 300 mph. This electronic sighting coincides with the visual sighting as far as area of sighting is concerned. No local air traffic at the time. Solution unknown." 188.
187. Duncanville, Texas. 18 August 52. No other source data. May be located in Air Force BLUE BOOK files by date: 19 August 52.