@book{25567,
	author = {Butler, G. M.},
	title = {Clays of eastern Colorado,},
	publisher = {The Smith-Brooks printing company,},
	year = {1915.},
	address = {Denver, Col.,},
	note = {"Partial list of the sources of data consulted in compiling the descriptions of the Colorado clay-bearing formations": p. 148-149.}
}