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Kaufmann، B.؛ Trapp، E.؛ Mezger، K. (2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt(Kellerwald, Germany)". The Journal of Geology. ج. 112 ع. 4: 495–501. Bibcode:2004JG....112..495K. DOI:10.1086/421077.
Sandberg، C.A.؛ Morrow، J.R.؛ Ziegler، W. (2002). "Late Devonian sea-level changes, catastrophic events, and mass extinctions". في Koeberl, C. and MacLeod, K.G. (المحرر). Catastrophic Events and Mass Extinctions: Impacts and Beyond: Boulder, Colorado(PDF). Special Paper. Geological Society of America. ج. 356. ص. 473–487. مؤرشف من الأصل في 2020-05-03. اطلع عليه بتاريخ 2019-09-05.{{استشهاد بكتاب}}: صيانة الاستشهاد: BOT: original URL status unknown (link) صيانة الاستشهاد: أسماء متعددة: قائمة المحررين (link)