Hjelmstad, K. E. <br/><br/>
Ultra low frequency electromagnetic fire alarm system for underground mines / 
by K.E. Hjelmstad and W.H. Pomroy. 
 - [Washing, D.C.] :  Bureau of Mines, U.S. Dept. of the Interior,  1991. 
 - 11 p. : ill. 
 - Report of investigations ; 9377 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>Mine fires--Prevention and control.<br/>Fire alarms.