@book{21170,
	author = {Argyle, R. W. },
	title = {Observing and Measuring Visual Double Stars},
	publisher = {Springer New York},
	year = {2012},
	series = {The Patrick Moore Practical Astronomy Series},
	address = {New York},
	edition = {2nd ed.},
	url = {http://doi.org/10.1007/978-1-4614-3945-5}
}