@book{25096,
	author = {Marshall, R. B. and Illinois State Geological Survey},
	title = {Results of spirit leveling in Illinois, 1909 and 1910 /},
	publisher = {Govt. Print. Off.,},
	year = {1911.},
	series = {U.S. Geological survey. Bulletin 493},
	address = {Washington,},
	note = {Includes index.}
}