Roof control strategies for underground coal mines / 
by William C. Smith. 
 - Avondale, Md. :  U.S. Dept. of the Interior, Bureau of Mines,  1993. 
 - 17 p. :  ill. 
 - Information circular ;  9351 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>Mines and mineral resources.<br/>Mine roof bolting.<br/>Mine roof control.<br/>Coal mines and mining.