Systematic timbering rules at the Washington coal mines /
| Prif Awdur: | |
|---|---|
| Fformat: | Dogfen y Llywodraeth Llyfr |
| Iaith: | English |
| Cyhoeddwyd: |
Washington, D.C. :
U.S. Dept. of Commerce, Bureau of Mines,
1930
|
| Cyfres: | Information circular (United States. Bureau of Mines) ;
6316 |
| Pynciau: |