Nikitin, I. F.; Popov, L. E. (1983). Middle Ordovician orthaceans and plectambonitaceans from north Priishim and the Reki Akzhar Basin in central Kazakhstan (Brachiopods). Ezhegodnik Vsesoyuznogo Paleontologicheskovo Obshchestva. 26: 228-247.
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Nikitin, I. F.; Popov, L. E.
1983
Middle Ordovician orthaceans and plectambonitaceans from north Priishim and the Reki Akzhar Basin in central Kazakhstan (Brachiopods)