Foord, A. H. (1887). On “Orthoceras [Endoceras] duplex,” Wahlenberg et auctt., with descriptions of three new species of Endoceras from the Ordovician of Sweden and Russia contained in the British Museum (Natural History). Annals and Magazine of Natural History. 20(120): 393-402.
On “Orthoceras [Endoceras] duplex,” Wahlenberg et auctt., with descriptions of three new species of<i> Endoceras </i>from the Ordovician of Sweden and Russia contained in the British Museum (Natural History)