@book{27595,
	author = {Leighton, Henry,},
	title = {Guidebook to the geology about Pittsburgh,},
	publisher = {Department of internal affairs, Topographic and geologic survey,},
	year = {1939.},
	series = {Bulletin G,},
	address = {Harrisburg, Pa.,},
	note = {At head of title: Pennsylvania Geological survey, Fourth series.}
}