Catatan

Bibliografi

• Bishop, Michael P.; Shroder, John F. (2004). Geographic Information Science and Mountain Geomorphology. Berlin New York: Springer Publishing. halaman 86–87. ISBN 978-3-540-42640-0. ISBN 354042640X. Dicapai pada 6 November 2010.
• Eberhart, Mark E. (2004). Why Things Break: Understanding the World by the Way it Comes Apart. New York: Random House, Harmony Books. m/s. 232. ISBN 978-1-4000-4883-0. Dicapai pada 6 November 2010.
• Harvey, Mark William Thornton; Simer, Peter (1999). The National Outdoor Leadership School Wilderness Guide: The Classic Handbook. New York: Simon & Schuster. m/s. 185. ISBN 978-0-684-85909-5. Dicapai pada 6 November 2010.
• The Geology of Snowdonia – A Collection of Historical Articles on the Physical Features of the Peaks of Snowdonia. City: Read Books Limited. 2013. m/s. 45. ISBN 978-1-4733-9043-0. Dicapai pada 18 January 2021. The word Bwlch is used in Welsh not only to signify a pass or easy route over a ridge, usually a depression between higher ground on either side, but also ...