Gaya APA
Tilling, R, I. (1980).
Eruption of Mount St. Helens : Past, Present, and Future .
Washington DC:
U.S. Government Printing Office.
Gaya MLA
Tilling, Robert, I..
"Eruption of Mount St. Helens : Past, Present, and Future".
Washington DC:
U.S. Government Printing Office,
1980.
Text.