Gaya APA
Survey, U, G. (1981).
Volcanic and Seismic Activity at Mount St. Helens August 1981 (August 1981).
Washington:
U.S. Geological Survey.
Gaya MLA
Survey, U.S., Geological.
"Volcanic and Seismic Activity at Mount St. Helens August 1981".
August 1981
Washington:
U.S. Geological Survey,
1981.
Text.