Vasilyeva et al., 2001
From dinoflaj3
Vasilyeva, O.N., Zhelezko, V.A. and Kozlov, V.A., 2001: Tavdinskaya (cheganskaya) svita Zauralya, ee vozrast po microfytoplanktonu i elasmobranchiyam, korrelyaciya s odnovozrastnimi otlozheniyami Zapadnoy Sibiri, Turgayskogo progiba. Materialy po stratigrafii i paleontologii Urala, Ekaterinburg, Issue 6, p.61-73, pl.1-3.