coal classification: References & Edit History
Article Contributors
Primary Contributors
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Otto C. Kopp
Professor Emeritus of Geological Sciences, University of Tennessee, Knoxville.
Other Encyclopedia Britannica Contributors
Article History
| Type | Description | Contributor | Date |
|---|---|---|---|
| Deleted table. | Jun 28, 2018 | ||
| Article revised and updated. | Mar 16, 2007 |
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