Gaya APA

Survey, U, G. (1981). Volcanic and Seismic Activity at Mount St. Helens January 1981 (January 1981). Washington: U.S. Geological Survey.

Gaya MLA

Survey, U.S., Geological. "Volcanic and Seismic Activity at Mount St. Helens January 1981". January 1981 Washington: U.S. Geological Survey, 1981. Text.