Areas nacionales de estudio ambiental :  una guía / 
National Park Service. 
 - [Washington, D.C.?] :  U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation,  [1972?] 
 - 51 p. :  ill. ;  26 cm. 
<br/><br/>Bibliography : p. 53-56. 
<br/><br/><br/>Español 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Conservation of natural resources--Study and teaching--United States.<br/>National environmental study areas.
<br/><br/><label>Dewey Class. No.: </label>370.193 
<br/><br/><label>GPO Item No.: </label>1972  0--469-236