@book{221671,
	author = {Gregersen, Erik},
	title = {Unmanned space missions :},
	publisher = {Britannica Educational Publishing; Rosen Educational services,},
	year = {2010.},
	series = {An explorer's guide to the universe},
	address = {New York:},
	note = {"In association with Britannica Educational Publishing and Rosen educational Services"}
}