Illinois State Geological Survey, Thiessen, G., Cady, G. H., Rees, O. W., & Reed, F. H. (1934). Contributions to the study of coal: A proposed simplification of the Parr unit coal formula.
Chicago Style (17th ed.) CitationIllinois State Geological Survey, Gilbert Thiessen, Gilbert H. Cady, Orin Wainwright Rees, and Frank Hynes Reed. Contributions to the Study of Coal: A Proposed Simplification of the Parr Unit Coal Formula. 1934.
MLA (9th ed.) CitationIllinois State Geological Survey, et al. Contributions to the Study of Coal: A Proposed Simplification of the Parr Unit Coal Formula. 1934.
Warning: These citations may not always be 100% accurate.