Postojalko 1990. [Towards the question of the boundary between the Lower and the Middle Carboniferous in the northern Urals.] Papulov, G.N.; Chuvashov, B.I.[Eds]. [The boundaries of biostratigraphical subdivisions of the Carboniferous in the Urals.], Ural'skoe otdelenie AN SSSR, Sverdlovsk, 1990: 1-176. Chapter pagination: 71-92, 173