Technological change and productivity in the bituminous coal industry 1920-60. 

 - Washington :  USDL ,  1961 
 - ii, 137p. ;  25 cm. 
 - Bulletin .
<br/><br/>Includes bibliographical references and index. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Coal resources<br/>Coal mining<br/>Productivity<br/>Technological change
<br/><br/><label>Dewey Class. No.: </label>333.82   / US