Falls of roof and coal in Washington mines

Author:	Ash, S. H.
Year:	1932
Document Type:	USBI
Issuing Agency:	U.S. Dept. of Commerce, Bureau of Mines,
SUDOC:	C 22.11:6617
Series:	Information circular / Bureau of Mines ;
Report Number:	6617
Subjects:	Mine roof control--Washington (State)
	Coal mines and mining--Washington (State)
Link:	https://hdl.handle.net/2027/mdp.39015086485474