Harris (2005), p. 179. (EN) S.L. Harris, Lassen Peak, in Fire Mountains of the West: The Cascade and Mono Lake Volcanoes, 3ª ed., Missoula, Mountain Press Publishing Company, 2005, ISBN0-87842-511-X.
Harris (2005), p. 185. (EN) S.L. Harris, Lassen Peak, in Fire Mountains of the West: The Cascade and Mono Lake Volcanoes, 3ª ed., Missoula, Mountain Press Publishing Company, 2005, ISBN0-87842-511-X.
Harris (2005), p. 182. (EN) S.L. Harris, Lassen Peak, in Fire Mountains of the West: The Cascade and Mono Lake Volcanoes, 3ª ed., Missoula, Mountain Press Publishing Company, 2005, ISBN0-87842-511-X.
Le fonti dissentono sul numero di circhi localizzati sul Broken Top; Wood e Kienle (1990) ne indicano tre (Wood e Kienle (1992), p. 181), ma Williams (1944) ne indica cinque intorno al cuore del vulcano Williams (1944), p. 45. (EN) Howel Williams, Volcanoes of the Three Sisters Region, Oregon Cascades, in Bulletin of the Department of Geological Sciences, vol. 27, n. 3, University of California Press, 1944. URL consultato il 31 luglio 2021.