Chitinozoan biostratigraphy in the Ordovician of Baltoscandia
Nõlvak, Jaak
2002
http://www.ester.ee/record=b1035650*est
Comparative morphological analysis of the early Paleozoic marine impact structures Kärdla and Neugrund, Estonia
Suuroja, Sten
2007
https://digi.lib.ttu.ee/i/?141
https://www.ester.ee/record=b2305374*est