1. V. V. Baltakis, “Sedimentary Formations and Lithologic Complexes of the Paleogene and Neogene in the Southern Baltic Region,” in Lithology and Geology of Mineral Deposits in the Southern Baltic Region (Mintis, Vilnius, 1966), pp. 277–321 [in Russian].
2. W. A. Berggren, “A Cenozoic Time Scale—Some Implications for Regional Geology and Paleobiogeography,” Lethaia 5(2), 195–215 (1972).
3. G. I. Egorov, “Late Eocene Foraminifers First Found in the Baltic Region,” Byull. Nauchno-Tekhn. Information MGiON SSSR 4(9), 6–7 (1957) [in Russian].
4. A. Eisenack, “Die Phosphoritknollen der Bernsteinformation als Uberlieferer tertiaren Planctons,” Schr. Phys.-ökon. Ges. Königsberg 70, 181–188 (1938).
5. A. Eisenack, “Mikrofossilien aus Phosphoriten des samlandischen Unteroligozans und uber die Einheitlichkeit der Hystrichosphaerideen,” Paleontographica Abt. A. 105(3–6), 49–95 (1954).