250 versus 500 volts or more for circuits in gassy coal mines

Author:	Ilsley, L. C.
Year:	1932
Document Type:	USBI
Issuing Agency:	U.S. Dept. of Commerce, Bureau of Mines,
SUDOC:	C 22.11:6556
Series:	Information circular / Bureau of Mines ;
Report Number:	6556
Subjects:	Coal mines and mining--Safety measures
	Electricity in mining
Link:	https://hdl.handle.net/2027/mdp.39015077561861