Contributions to the study of coal: A proposed simplification of the Parr unit coal formula - Illinois State Geological Survey; Thiessen, Gilbert, 1905-; Cady, Gilbert H. (Gilbert Haven), 1882-; Rees, Orin Wainwright, 1898-; Reed, Frank Hynes, 1890- (Urbana, Illinois, Printed by authority of the state of Illinois, 1934)
At head of title: State of Illinois. Department of Registration and Education. Division of the State Geological Survey.
Keywords: Coal -- Analysis; Coal -- Illinois