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Summary
| Description |
English: Origional caption: "Fig. 36. Block system of Retreating Long-wall, West Virginia." Plan of a multi-panel longwall retreat mine, circa 1917. Edge detection has been used to convert the figure to a line drawing. |
| Date | |
| Source | Percentage of Extraction on of Bituminous Coal with Special Reference to Illinois Conditions, Engineering Experiment Station Bulletin No. 100, University of Illinois, page 115. |
| Author | C. M. Young |
Licensing
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
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File history
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 15:54, 20 August 2009 | | 768 × 821 (60 KB) | Douglas W. Jones | {{Information |Description={{en|1=Origional caption: "Fig. 36. Block system of Retreating Long-wall, West Virginia." Plan of a multi-panel longwall retreat mine, circa 1917. Edge detection has been used to convert the figure to a line drawing.}} |Sour |
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