Gaya APA

Ewert, J, W. (1992). Monitoring Volcanoes : Techniques and Strategies Used by The Staff of The Cascades Volcano Observatory, 1980-90 . Washington DC: United States Government Printing Office.

Gaya MLA

Ewert, John, W.. "Monitoring Volcanoes : Techniques and Strategies Used by The Staff of The Cascades Volcano Observatory, 1980-90". Washington DC: United States Government Printing Office, 1992. Text.