Gaya APA
Johnston, D, A. (1983).
February 1983 Monthly Report Mount St. Helens (Tahun 1983).
Bandung:
U.S Geological Survey.
Gaya MLA
Johnston, David, A..
"February 1983 Monthly Report Mount St. Helens".
Tahun 1983
Bandung:
U.S Geological Survey,
1983.
Text.