TY  - BOOK
ED  - U. S. Department of the interior. National Park Service
ED  - United States.
TI  - Areas nacionales de estudio ambiental: una guía 
U1  - 370.193 23
PY  - 1972///?]
CY  - [Washington, D.C.?]
PB  - U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation
KW  - Conservation of natural resources
KW  - Study and teaching
KW  - United States
KW  - National environmental study areas
N1  - Bibliography : p. 53-56
ER  -