@book{26988,
	author = {Wybergh, W. and South Africa.},
	title = {The building stones of the Union of South Africa /},
	publisher = {The Government Printer,},
	year = {1932.},
	series = {Geological Survey memoir ;},
	address = {Pretoria :},
	note = {At head of title: Union of South Africa. Department of Mines and Industries.}
}