Penrose, Ray G. <br/><br/>
Laboratory study of self-sealing limestone plugs for mine openings / 1973 
Ray G. Penrose and Igor Holubec 
 - Washington :  U.S. Government Printing Office,  1973 
 - xx, 217 p. :  ill. ;  28 cm. 
 - Environmental protection series .
<br/><br/> EPA-670/2-73-081 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Mine<br/>Pollution
<br/><br/><label>Dewey Class. No.: </label>553.516