Dressel, W.M. <br/><br/>
Inverted pyramid-shaped plugs for closing abandoned mine shafts Galen, K.S., demonstration project 
Dressel, W.M. 
 - Washington  Bureau of mines  198 
<br/><br/><label>Subjects--Topical Terms: </label><br/>MINERIA<br/>MINAS ABANDONADAS
<br/><br/><label>Universal Decimal Class. No.: </label>622.228