Tryon, F.G. <br/><br/>
Coal in 1919, 1920 and 1921. 

 - Washington, D.C.  Government Printing Office  1923 
 - pp. 445-662 
 - Mineral Resources of the United States, 1921-Part II .
<br/><br/> Impreso  En biblioteca 2 ejemplares. 
<br/><br/><br/>Ingles 
<br/><br/><label>Subjects--Topical Terms: </label><br/>MINERIA<br/>CARBON
<br/><br/><label>Dewey Class. No.: </label>553.2