Click on the links below to read some writeups about occurrence of UFO Sightings.No matter Whether the Sightings are illusory or real there is a specific combination which causes the sightings.Read to know more :
http://horasarvam.blogspot.in/2012/07/ufo-crash-at-roswellmexicoin-1947its.html
http://horasarvam.blogspot.in/2012/05/carson-sink-ufo-incident-1952.html
http://horasarvam.blogspot.in/2012/05/ufo-arnold-sighting.html
http://horasarvam.blogspot.in/2012/05/alderney-ufo-sighting-23-rd-april-2007.html
http://horasarvam.blogspot.in/2012/05/battle-of-los-angeles-ufo-sightings.html
http://horasarvam.blogspot.in/2012/05/tehran-ufo-incident.html
http://horasarvam.blogspot.in/2012/05/mystery-of-ufo-over-dome-of-rock.html
http://horasarvam.blogspot.in/2011/12/ufo-spotted-near-to-mercury.html
http://horasarvam.blogspot.in/search/label/UFO%20s