| Author: | Mitchell, George W. | 
|---|---|
| Additional Authors: | Johnson, A. C. | 
| Year: | 1949 | 
| Document Type: | USBI | 
| Issuing Agency: | U.S. Dept. of the Interior, Bureau of Mines, | 
| SUDOC: | I 28.27:7495 | 
| Series: | Information circular / United States Department of the Interior, Bureau of Mines ; | 
| Report Number: | 7495 | 
| Subjects: | Shaft sinking--Costs | 
| Mining engineering | |
| Shaft sinking--Technique | |
| Link: | https://hdl.handle.net/2027/mdp.39015078463752 |