@book{27686,
	author = {Grim, Ralph E. and Schubert, Carl Edward,},
	title = {(1) Elements of the petrographic study of bonding clays and of the clay substance of molding sands},
	year = {1940.},
	series = {Illinois. State geological survey. Report of investigations},
	address = {Urbana, Ill.,},
	note = {At head of title: State of Illinois ... Department of registration and education ... Division of the State geological survey ...}
}