Bibliography: Famous Astronomers - Charles Messier: http://famousastronomers.org/charles-messier/ Space.com: http://www.space.com/16686-charles-messier-biography.html The Messier Catalogue - Biography: http://messier.seds.org/xtra/history/biograph.html Famous Astronomers - Carl Sagan: http://famousastronomers.org/carl-sagan/ Biography.com - Carl Sagan: http://www.biography.com/people/carl-sagan-9469191 Famous Scientists - Carl Sagan: http://www.famousscientists.org/carl-sagan/
