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Montañez, Isabel Patricia (2 Aralık 2021). "Current synthesis of the penultimate icehouse and its imprint on the Upper Devonian through Permian stratigraphic record". Geological Society, London, Special Publications. Cilt 512. ss. 213-245. doi:10.1144/SP512-2021-124.
Hogan 2010. Hogan, C. Michael (2010). "Fern". Encyclopedia of Earth. Washington, DC: National council for Science and the Environment. 9 Kasım 2011 tarihinde kaynağından arşivlendi.
Hogan 2010. Hogan, C. Michael (2010). "Fern". Encyclopedia of Earth. Washington, DC: National council for Science and the Environment. 9 Kasım 2011 tarihinde kaynağından arşivlendi.
Conybeare & Phillips 1822, p. 323: "Book III. Medial or Carboniferous Order.". Conybeare, W. D.; Phillips, William (1822). Outlines of the geology of England and Wales : with an introductory compendium of the general principles of that science, and comparative views of the structure of foreign countries. Part I. Londra: William Phillips. OCLC1435921.