Mine communications. Proceedings: Bureau of mines Technology Transfer Seminar, Bruceton, Pa., March 21-22, 1973 
U.S. Bureau of mines. 
 - Washington  Bureau of mines.  1974 
<br/><br/><label>Subjects--Topical Terms: </label><br/>MINERIA
<br/><br/><label>Universal Decimal Class. No.: </label>622