How are men killed in mines by falls of roof and coal?

Author:	Paul, J. W.
Year:	1927
Document Type:	USBI
Issuing Agency:	U.S. Dept. of Commerce, Bureau of Mines,
SUDOC:	C 22.11:6035
Series:	Information circular / Bureau of Mines ;
Report Number:	6035
Subjects:	Mining engineering
	Coal mines and mining--Safety measures
Link:	https://hdl.handle.net/2027/mdp.39015086471367