Antsygin 1970. [A trilobite of the family Pterygometopidae from the Ordovician deposits of the Urals.]. Breivel', M.G.; Palulov, G.N.[Eds]. [Materials on the palaeontology of the Urals.] Akad. Nauk USSR Ural Filial. lnst. Geol. Geoch. l-195, 39 pls. 1970., Sverdlovsk., 1970: 13-42. Chapter pagination: 13-42