|| Givulescu,R. The fossil flora of Roumania; Second Supplement, first Part.
|| Akhmeteev,M.A. et al. Upper Eocene Oligocene spore and pollen, plant macrofossils and phytoplankton in stratotypes of Tchegan and Astsheairyk Formations (North Usturt, Kazakhstan).
|| Krasheninnikov,V.A. et al. Reference sections of the Eocene - Oligocene boundary strata on the territory of the former Soviet Union. The Northern Ustyurt sections (the Sandal Mountain and Aszeiryk Ravine, Western Kazakhstan). (In: Late Eocene-Early Oligocene geological and Biotical events on the Territory of the Former Soviet Union.Part 2: the regional geology of the Upper Eocene and ower Oligocene. V.A.Krasheninnikov and M.A.Akhmetiev, editors)