United States. Federal Bureau of Investigation, Federal Bureau of Investigation FOIA Documents - Unidentified Flying Objects
“ BUREAU BULLETIN No. 42 Series 1947 You should investigate each instance which is brought to your attention of a sighting of a flying disc in order to ascertain whether or not it is a bona fide sighting, an imaginary one or a prank. You should also bear in mind that individuals might report seeing flying discs for various reasons. It is conceivable that an individual might be desirous of seeking personal publicity, causing hysteria, or playing a prank. ”
