 |
|
Figures 2-9: Barrier Pillars in the Western Middle Field: Anthracite Region of Pennsylvania
| Year: | 1953 |
|---|---|
| Document Type: | N/A |
| Issuing Agency: | United States. Bureau of Mines. |
| Series: | United States Bureau of Mines Reports |
| Report Number: | Bulletin 521 |
| Link: | https://digital.library.unt.edu/ark:/67531/metadc1855810/ |
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