Pozdnepermskiĭ ėtap ėvol︠i︡u︠t︡sii organicheskogo mira : midiĭskiĭ ︠i︡arus SSSR - Kotl︠i︡ar, G. V.; Zakharov, ︠I︡U. D. (︠I︡Uriĭ Dmitrievich), d-r geol.-miner. nauk ("Nauka," Leningradskoe otd-nie, 1989)