	Authors	Year	Title
	Boardman & Work	2004	Stratigraphic distribution of the ammonoids Shumardites and Vidrioceras and implications for the definition of the global Gzhelian Stage, Upper Pennsylvanian Series, Upper Pennsylvanian Series. Newsletter on Carboniferous Stratigraphy, 22: 23-27, 2 fig.
	Elias	1938	Studies of Late Paleozoic ammonoids. Journal of Paleontology, 12 (1): 86-100, pl.19,20; Tulsa,Oklahoma.
	Frebold	1932	Marines Unterperm in Ostgrönland und die Frage der Grenzziehung zwischen dem pelagischen Oberkarbon und Unterperm. Medd. Gronld. ud. Komm. vid. und. Gronld., 84 (4): 1-35, fig.1-4, pl.1; Kobnhaven.
	Schmidt	1929	Tierische Leitfossilien des Karbon. Gürich,G.: Leitfossilien, 6. Lief.: 1-107, pl.1-23; Berlin (Borntraeger).
	Smith	1903	The Carboniferous Ammonoids of America. Monography, U.S. geological Survey, 42: 1-211, pl.1-29; Washington.
	Tharalson	1984	Revision of the Early Permian ammonoid family Perrinitidae. Journal of Paleontology, 58 (3): 804-833, fig.1-24, 1tab.; Lawrence, Kansas.