Hays, Samuel P <br/><br/>
Conservation and the gospel of efficiency :  the progressive conservation movement, 1890-1920 / 
Samuel P. Hays 
 - Cambridge, Mass. :  Harvard University Press,  1959 
 - 297 p. ;  21 cm. 
 - Harvard historical monographs 40 .
<br/><br/>'Bibliographical note': p. 277-282. Bibliographical footnotes 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Conservation of natural resources--United States--History<br/>Environmental policy--United States--History