Akinin et al. 2019

Akinin V.V., Golovneva L.B., Salnikova E.B., Anisimova I.V., Shczepetov S.V., Nosova N.V. The composition and age of the Ul'ya flora (Okhotsk-Chukotka volcanic belt, north-east of Russia): paleobotanical and geochronological constraints // Acta Palaeobotanica. 2019. V. 59. No 2. P. 251-276.