Conservation in the United States / 
by A. F. Gustafson ... [et al.]. 
 - 3rd ed. 
 - Ithaca :  Comstock Publishing Associates,  1949. 
 - ix, 534 p. :  ill., maps. ;  24 cm. 
<br/><br/>'Selections for supplementary reading': p. 513-520. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Natural resources.
<br/><br/><label>Subjects--Geographic Terms: </label><br/>United States--Economic conditions.