Hartwig, G. . <br/><br/>
Workers under the Ground or Mines and Mining /  Textual Documents 
G. Hartwig. 
 - 1st ed. / 
 - London :  Longmans Green & Co. ,  1893. 
 - ix,126p. :  ill ;  18cm . 
<br/><br/><label>Subjects--Index Terms: </label>Geology Coal Mines and Mining G-Geology 
<br/><br/><label>Dewey Class. No.: </label>550  / H 259 W