Ashworth, W. (1977). Hells Canyon, the deepest gorge on earth. Hawthorn Books.
Cita Chicago Style (17a ed.)Ashworth, William. Hells Canyon, the Deepest Gorge on Earth. New York: Hawthorn Books, 1977.
Cita MLA (8a ed.)Ashworth, William. Hells Canyon, the Deepest Gorge on Earth. Hawthorn Books, 1977.
Precaución: Estas citas no son 100% exactas.