@book{231885,
	author = {Grego, Peter. and ebrary, Inc.},
	title = {Venus and Mercury, and how to observe them},
	publisher = {Springer,},
	year = {c2008.},
	series = {Astronomers' observing guides},
	address = {New York :},
	url = {http://site.ebrary.com/lib/rucke/Doc?id=10217562}
}