@book{26621,
	author = {Thwaites, F. T.},
	title = {Stratigraphy and geologic structure of Northern Illinois,},
	publisher = {Jeffersons Printing and Stationery Co.]},
	year = {1927.},
	address = {Urbana, Illinois},
	note = {At head of title: State of Illinois. Department of Registration and Education. Division of the State Geological Survey.}
}