Coal balls as an index to the constitution of coal
By: by James M. Schopf
Series: Circular / Illinois State Geological Survey -- no. 51; Circular (Illinois State Geological Survey) -- no. 51.
Publisher: State Geological Survey
Published: 1939
Place of publication: Urbana, Ill
Language: eng
Number of pages: 189
Subjects: Coal; Coal balls; Analysis
Notes: Cover title.

"Reprinted from the Transactions, Illinois State Academy of Science, vol. 31, no. 2, pp. 187-189, 1939."

Includes bibliographical references.